Bicycle dropper seat post assembly with a bottom mounted gas spring cartridge

ABSTRACT

A dropper post assembly can include an outer tube and an inner tube with a lower end that is within the outer tube and include a tube engagement. A spring cartridge assembly can include: a cartridge tube providing a cylinder; a piston movably received within the cylinder to provide a first chamber a lower side of the piston and a second chamber between the piston; a cartridge rod; and a second engagement member configured to releasably engage the tube engagement member thereby fastening the cartridge tube to the lower end of the inner tube so that the cartridge tube is axially fixed to the inner tube and movable with the inner tube relative to the outer tube.

CROSS REFERENCE TO RELATED APPLICATION

The present application claims priority to and the benefit of U.S.provisional patent application No. 63/329,444, filed Apr. 10, 2022, andentitled Bicycle Dropper Seat Post Assembly with A Bottom Mounted GasSpring Cartridge, the entirety of which is incorporated herein byreference.

TECHNICAL FIELD

The present invention relates to a locking spring cartridge used tocontrol the height of a dropper seat post on a bicycle, and a dropperpost assembly including the same, and more specifically to a dropperseat post assembly that can include a novel cartridge assembly designand in which a lower end of the cartridge tube, rather than its upperend, is secured to the seat post tube to axially restrain the cartridgetube relative to the seat post tube.

INTRODUCTION

U.S. Pat. No. 5,881,988 discloses a seat assembly includes a seat tubein which a seat post is movably received therein which has a clampingmember with a seat disposed thereto. The seat post has two plainportions defined diametrically opposite in an outer periphery thereofand the seat tube has two wedge-shaped recesses defined diametricallyopposite in an inner periphery thereof so as to receive two wedge-shapedblocks therein. The seat post extends through a nut member which isthreadedly mounted to the seat tube.

U.S. Patent Publication No. 2020/070913 discloses a bicycle seat postassembly in which the travel distance of the seat post can be adjusted.The seat post assembly includes an outer tube that is configured totelescopically receive an inner tube. The inner tube is axially slidablerelative to the outer tube between a retracted position and an extendedposition, the extended position being determined by an extensionassembly in which an inner contact member engages an outer contactmember, thereby setting the upper limit of axial extension of the innertube. The extension of the inner tube can be limited to an intermediateposition that lies between the retracted and extended positions by aninsertable shim that is positionable between the inner and outer contactmembers.

Taiwan patent publication no. TW201801969A discloses a casing gapfilling structure for a bicycle seat tube, which comprises a casing sethaving an outer tube and an inner tube which are sleeved onto each otherand move linearly; a rotation constraining set which is arranged betweenthe inner tube and the outer tube and provided with a first constraininggroove arranged on the inner diameter edge of the outer tube and asecond constraining groove arranged on an outer diameter edge of theinner tube, the first and second constraining grooves forms aconstraining space together, and at least one metal constraining membermade of a metal material is accommodated in the constraining space andcapable of conducting synchronous linear displacement with the innertube; a gap filler set is disposed in the constraining space andprovided with at least one plastic constraining member made of a plasticmaterial, the gap filler set and the metal constraining memberrespectively overlapping with each other in the constraining space alongthe axial direction of the inner and outer tubes, and the plasticconstraining member is able to effectively fill the constraining spaceso as to eliminate the gaps among the plastic constraining member andthe first and second constraining grooves; in this way, the rotationconstraining set and the gap filler set are used to achieve the dualfunction of constraining the rotation and eliminating the gaps betweenthe inner tube and the outer tube at the same time. The manufacturingcost of the filling structure is low because the overall components aresimple and easy to be assembled quickly. Further, the gaps among thecomponents generated by the fit tolerance and the manufacturingtolerance are reduced with no requirement of tight rotation actions, theautomatic filling function is thus achieved and compatible with thelifting seat tube and the suspension seat tube.

U.S. Pat. No. 10,974,781 discloses a bicycle seat post assembly in whichthe travel distance of the seat post can be adjusted. The seat postassembly includes an outer tube that is configured to telescopicallyreceive an inner tube. The inner tube is axially slidable relative tothe outer tube between a retracted position and an extension position,the extension position being determined by an extension assembly inwhich a slider engages an upper retainer surface, thereby setting theupper limit of axial extension of the inner tube. The extension of theinner tube can be limited to an intermediary extension position thatlies between the retracted and extension positions by an insertableextension stopper that is positionable under the upper retainer surface.

Taiwan utility model publication no. TWM517710U discloses a bicycle gashydraulic seat tube assembly related to bicycles, especially a bicyclehydraulic pressure seat tube assembly. The common gas-oil seat tubeadopts the gas compressible characteristic to match the flow ofhydraulic oil in the space, so that the relative position change betweenthe seat tube and the seat post is achieved, thereby achieving theeffect of adjusting the height of the seat cushion. For example, asdisclosed in the Republic of China Announcement No. M332057, the upperand lower displacements of the valve stem are used to switch the flowstate of the adjustment flow path, so that the seat tube can achieve theeffect of adjusting the height. However, in the aforementioned patentcase, the inner and outer spaces for storing the hydraulic oil aredisposed between the relatively exposed seat tube and the adjustmentseat and are not located in the relatively closed riser. The risk ofleakage is therefore necessary for structural improvements. The mainpurpose of this creation is to provide a bicycle gas pressure seat tubeassembly that reduces the risk of oil and gas leakage.

Taiwan utility model publication no. TWM513153 shows a post in which alifting adjustment unit 40 is housed inside seatpost 30 and secured bythreadedly engaging lower end cap 48 to the lower end of seatpost 30. Anexternal air chamber 60 is formed between seat post 30 and tube body 49that is in fluid communication with internal air chamber 66 via lowerair holes 482. External air chamber 60 can further fluidly communicatewith an air valve on upper end cover 47 via upper air hole 472. Bothlower end cap 48 and upper end cap 47 are o-ring sealed to seat tube 30so that air pressure held in external air chamber 60 and internal airchamber 66 cannot escape to atmosphere. As such if lifting adjustmentunit 40 is removed from and reinstalled into seat post 30, byunthreading lower end cap 48, the gas pressure would be lost, and thesystem would need to be recharged via the air valve on upper end cap 47.

SUMMARY

Dropper seat posts are telescopic posts that allow the rider to changethe height of their seat without having to stop and adjust amechanically tightened seat post collar. It can be generallyadvantageous to lower the bicycle seat as far as possible when ridingthrough technical terrain to allow the rider to change body position orbend their knees deeply without contacting the seat.

Some known dropper post locking spring cartridges are configured withtwo or more chambers containing liquid (i.e., hydraulic oil), gas (i.e.,air) or a combination thereof. There is typically an internal pistonvalve controlled by an actuator/remote and an actuation rod translatablebetween an open and a closed position. When the piston valve is closedand a rider sits on a seat attached to the top of the post, the chambercontaining, by design, only oil is placed in compression therebyallowing the post to be loaded without retracting.

In this configuration, when the piston valve is opened the pistontravels into the oil only chamber. Because the oil in the oil onlychamber is substantially incompressible it is typically more difficultto open the valve while the upper tube is being urged toward theretracted position. This causes the rider to have to exert more force onthe actuator/remote than may be comfortable, and/or that may putunwanted loads on the actuator system, to overcome this resistance andopen the valve.

In this configuration, if the rider sits down on the seat too fast/hardwhile the piston valve is locked (closed), for example if a rider wereto have one or both feet slip off the pedals and fall onto the seat withsubstantially all of their body weight, the seat post would generallynot retract and therefore the seat would not move/lower to absorb andthe rider could be injured by the seat and/or cause damage to thedropper post or seat.

Also, in this configuration air can sometimes enter the oil only chamberunintentionally. Once there, the presence of the relatively compressibleair/gas within the chamber that is intended to contain only oil/liquidmay allow the post to compress slightly under a relatively low forcewhile the piston valve is, and remains, locked. This relatively lowforce sponginess is seen by consumers as being generally undesirable andas an indicator of a low-quality design. Correcting and a generallyexpensive and/or complicated rebuild is required to fix the problem.

In view of some of the shortcomings of the known dropper posts,including those known designs referred to herein, there remains ageneral desire for a sealed locking spring cartridge that can be used ina dropper post assembly and that can be installed or removed withoutrequiring the removal of the seat clamps. This may allow the springcartridge to be serviced, replaced or otherwise accesses withoutrequiring the removal of the seat clamps and the seat any seat that isattached.

There also remains a general desire for a sealed locking springcartridge that can be constrained to the lower end of the seat postinner tube rather than the upper end of the seat post inner tube, andpreferably regardless of the relative difference between the seatpostinner tube inner diameter and the cartridge outer tube outer diameter.This could allow the sidewalls of the seat post inner tube to bemodified to help achieve other desirable functions/attributes (such asincreased strength or reduced weight) without requiring significantmodification or redesign of the spring cartridge. This could help allowa common spring cartridge to be used with two or more different seatpostinner tube designs.

There also remains a general desire for a sealed locking springcartridge that does not require a threaded hole or protrusion at the topend of the seatpost inner tube. This can help facilitate the use ofclosed-top seatpost inner tube. Using a closed-top seatpost inner tubemay help simply manufacturing of the seatpost inner tube, may modify itsstrength or other parameters and/or may help provide a more sealedarrangement that can prevent dirt or other debris from getting into theinterior of the seatpost inner tube via the opening that would otherwisebe required to accommodate the upper fastener on conventional springcartridges.

There also remains a general desire for a sealed locking springcartridge that can be removed and reinstalled into the seatpost innertube without having the recharge the gas pressure in the system. Thiscan simplify and the maintenance and/or assembly of the dropper postassemblies and may allow portions of the dropper post assembly to beserviced by a user and/or without the need for specialized tools andequipment that could be required to open a pressurized spring cartridgeand/or recharge the cartridge once installed.

In accordance with one broad aspect of the teachings described herein, adropper post assembly for supporting a bicycle seat may include an outertube extending axially along a post axis between a lower end and anupper end and an inner tube extending axially between an upper end thatis connectable to a bicycle seat and a lower end that is disposed withinthe outer tube and has a tube engagement member. The inner tube may beaxially movable relative to the outer tube between an extended positionand a retracted position. A spring cartridge assembly may beconfigurable in an unlocked configuration in which the spring cartridgeassembly biases the inner tube toward its extended position and a lockedconfiguration. The spring cartridge assembly may include a cartridgetube providing a cylinder and being disposed within and movable with theinner tube. The cartridge tube may extend between an upper end disposedat the upper end of the inner tube and a lower end that is disposed atthe lower end of the inner tube. A lower seal assembly may be disposedat a lower end of the cartridge tube and may seal a lower end of thecylinder. A piston may be movably received within the cylinder toprovide a first chamber defined between the piston and the lower sealassembly and disposed on a lower side of the piston, and a secondchamber between the piston and an upper end of the cylinder and disposedon an opposing, upper side of the piston. Moving the inner tube towardthe retracted position may expand the first chamber, the piston mayinclude including a valve that is configurable in an open position inwhich fluid communication is established between the first chamber andsecond chamber and the spring cartridge assembly is in the unlockedconfiguration, and a closed position in which the first chamber isfluidly isolated from the second chamber and the spring cartridgeassembly is in the locked configuration. A cartridge rod may extendaxially through the lower seal assembly between an inner end engagingthe piston and an outer lower end at the lower end the outer tube. Asecond engagement member may be configured to releasably engage the tubeengagement member thereby fastening the cartridge tube to the lower endof the inner tube so that the cartridge tube may be axially fixed to theinner tube and movable with the inner tube relative to the outer tube.An actuator may have a body disposed adjacent the outer end of thecartridge rod and being operable to actuate the valve to change thespring cartridge assembly between the locked configuration and theunlocked configuration.

The cartridge tube may be axially removable via the lower end of theinner tube when the second engagement member is disengaged from the tubeengagement member and the spring cartridge assembly remains operationwhen removed from the inner tube.

The tube engagement member may be integrally formed on an inner surfaceof the inner tube, and preferably comprises threads formed in the innersurface of the inner tube.

The upper end of the cartridge tube does may not include a fasteningmechanism engaging the inner tube in a manner that restrains axialmovement of the cartridge relative to the inner tube.

An axially upper most portion of the spring cartridge may be disposedwithin the inner tube and does not extend axially beyond the upper endof the inner tube, whereby an entirety of the spring cartridge isdisposed axially inboard of the upper end of the inner tube.

The inner tube may include an upper end wall that covers the upper endof the inner tube, and the cartridge tube may include an axially facingupper cap surface that opposes the upper end wall when the cartridgetube is disposed within the inner tube. The upper cap surface and upperend wall may be complimentary to each other and generally planar and thecartridge tube may be located axially inboard of the upper end wall.

An openable seat clamp assembly may be connected to the upper end of theinner tube and may be configured to releasably retain a bicycle seat.The second engagement member may be disengageable from the tubeengagement member so that the spring cartridge can be removed from theinner tube without opening the seat clamp assembly.

When the spring cartridge is axially removable via the lower end of theinner tube after disengaging the second engagement member from the tubeengagement member and wherein the cylinder remains sealed, and thespring cartridge assembly remains operable when the spring cartridgeassembly is removed from the inner tube.

A fastening member may be removably insertable in the lower end of theinner tube. The fastening member may include the second engagementmember and an abutment surface, wherein when the fastening member isinserted so that the second engagement member engages the tubeengagement member the cartridge tube is compressed axially between theabutment surface and the upper end of the inner tube.

The fastening member may include a captive sidewall extending axiallyfrom the abutment surface and cooperating with the abutment surface toat least partially define a tube recess sized to accommodate the lowerend of the cartridge tube. When the fastening member is inserted, thecaptive sidewall may be disposed laterally between the cartridge tubeand the inner tube.

The captive sidewall may surround the tube recess and may define arecess diameter that is substantially the same as an outer diameter ofthe cartridge tube so that the and lateral movement of the lower end ofthe cartridge tube relative to the fastening member and the lower end ofthe inner tube is inhibited cartridge tube is closely/snugly in the tuberecess so that when the fastening member is inserted lateral movementbetween the lower end of the cartridge tube and the lower end of theinner tube is inhibited.

The second engagement member may be disposed toward a lower end of thefastening member and the abutment surface may be disposed toward anopposing, upper end of the fastening member.

An inner surface of the lower end of the fastening member may include adrive portion configured to be engaged by a corresponding driving toolused to secure the fastening member within the inner tube.

Optionally, when the fastening member is inserted, it may be at leastpartially axially nested within the inner tube, and preferably when thefastening member is inserted it is entirely axially nested within theinner tube.

An openable seat clamp assembly may be connected to the upper end of theinner tube and may be configured to releasably retain a bicycle seat.The fastening member may be insertable and removable from the inner tubeindependently from opening the seat clamp assembly, whereby the secondengagement member is disengageable from the tube engagement memberwithout opening the seat clamp assembly.

The inner tube may include an upper captive portion at its upper endhaving a first internal diameter that is substantially the same as anouter diameter of the cartridge tube so that the upper end of thecartridge tube is closely/snugly received in the upper captive portionbut remains axially removable and lateral movement between the cartridgetube and the inner tube is inhibited.

The inner tube may include a clearance portion axially inboard from theupper captive portion and having a second internal diameter that isgreater than the first internal diameter and the outer diameter of thecartridge tube, whereby an annular gap may be formed within theclearance portion between an outer surface of the cartridge tube and anopposing inner surface of the inner tube.

A bumper may be positioned laterally between the cartridge tube and theinner tube within the annular gap and inhibiting lateral movement of thecartridge tube relative to the inner tube.

The bumper may laterally encircle the cartridge tube and may have alength in the axial direction that is less than 20% of an axial lengthof the cartridge tube.

The bumper ay be located within an axially middle portion of thecartridge tube, and optionally may be located at the axial midpoint ofthe cartridge tube.

The lower end of the inner tube may include an engagement region thatincludes the tube engagement member and has a third internal diameterthat is greater than the second internal diameter.

The inner diameter of the inner tube may increase from its upper end toits lower end.

The inner engagement member may be formed on an outer surface of thecartridge tube.

The first chamber may contain substantially only a liquid and the secondchamber may contain a mixture of a liquid and a gas. When the dropperpost assembly is oriented so that the second chamber is above the firstchamber the spring cartridge assembly may operate as a self-bleedingcartridge, in which when the valve is in its open position gas containedin the first chamber escapes through the valve and is collected in thesecond chamber.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view of one example of a dropper post in a retractedposition;

FIG. 2 is a side view of the dropper post of FIG. 1 in an extendedposition;

FIG. 3 is a partially exploded view of the dropper post of FIG. 1 ;

FIG. 4 is a cross-sectional view of the dropper post of FIG. 2 , takenalong line 4-4;

FIG. 5 is an enlarged view of a portion of the cross-sectional view ofFIG. 4 ;

FIG. 6 is a cross-sectional view of another example of a dropper post;

FIG. 7 is an enlarged view of a portion of the cross-sectional view ofFIG. 6 ;

FIGS. 8 and 9 are enlarged views of another portion of thecross-sectional view of FIG. 6 ;

FIGS. 10-13 are additional cross-sectional views of dropper post of FIG.6 ; and

FIG. 14 is a cross-sectional view of a portion of the dropper post ofFIG. 12 , taken along Plane A;

FIG. 15 is a graph showing M_(F) vs (D_(S)/D_(R));

FIG. 16 is a partial cutaway view of one example of a dropper postassembly in which a spring cartridge is mounted in a manner that isknown in the prior art;

FIG. 17 is a side view of another example of a dropper post assembly;

FIG. 18 is a partial section view of the dropper post assembly of FIG.17 , taken along line 18-18 to reveal the interior of the post innertube and post outer tube;

FIG. 19 is a further section view of the dropper post assembly of FIG.17 , revealing the interior of the locking gas spring cartridge;

FIG. 20 is an enlarged view of a portion of FIG. 19 ;

FIG. 21 is a further section view of the dropper post assembly of FIG.17 , revealing the interior of the locking gas spring cartridge in adifferent configuration;

FIG. 22 is an enlarged view of a portion of FIG. 21 ;

FIG. 23 is a perspective view of one example of a locking gas springcartridge from below;

FIG. 24 is a perspective view of the locking gas spring cartridge ofFIG. 24 from above;

FIG. 25 is a perspective view of one example of a lockring from below;

FIG. 26 is a perspective view of the lockring of FIG. 25 from above;

FIG. 27 is a perspective view of one example of a driving tool form oneside;

FIG. 28 is a perspective view of the driving tool of FIG. 27 from above;

FIG. 29 is a partially exploded view of the dropper post assembly ofFIG. 17 ;

FIG. 30 is another partially exploded view of the dropper post assemblyof FIG. 17 ;

FIG. 31 is a partial cross-section view of the dropper post assembly ofFIG. 17 ;

FIG. 32 is an enlarged view of a portion of FIG. 31 ;

FIG. 33 is an enlarged view of a portion of FIG. 32 ;

FIG. 34 is an enlarged view of a portion of FIG. 31 ;

FIG. 35 is a partial cross-section view of another example of a dropperpost assembly;

FIG. 36 is an enlarged view of a portion of FIG. 35 ;

FIG. 37 is an enlarged view of a portion of FIG. 36 ;

FIG. 38 is an enlarged view of a portion of FIG. 35 ;

FIG. 39 is a perspective view of another example of a locking gas springcartridge assembly;

FIG. 40 is a partial cross-section view of a dropper post assembly in alocked configuration;

FIG. 41 is an enlarged view of a portion of FIG. 40 ;

FIG. 42 is the partial cross-section view of a dropper post assembly ofFIG. 40 in an unlocked configuration; and

FIG. 43 is an enlarged view of a portion of FIG. 42 .

DESCRIPTION

Various apparatuses or processes will be described below to provide anexample of an embodiment of each claimed invention. No embodimentdescribed below limits any claimed invention and any claimed inventionmay cover processes or apparatuses that differ from those describedbelow. The claimed inventions are not limited to apparatuses orprocesses having all the features of any one apparatus or processdescribed below or to features common to multiple or all of theapparatuses described below. It is possible that an apparatus or processdescribed below is not an embodiment of any claimed invention. Anyinvention disclosed in an apparatus or process described below that isnot claimed in this document may be the subject matter of anotherprotective instrument, for example, a continuing patent application, andthe applicants, inventors or owners do not intend to abandon, disclaim,or dedicate to the public any such invention by its disclosure in thisdocument.

Bicycle dropper seatposts allow a rider to change the height of theirseat while riding without having to stop and adjust a mechanicallytightened seat post collar. Dropper seat posts are available indifferent sizes, having different lengths of travel and differentminimum and maximum seat heights. The dropper posts can include a loweror outer tube that can be connected to a bicycle, and an upper or innertube that is telescopically slidable relative to the outer tube. Abicycle seat is connectable to the upper end of the inner tube, using asuitable clamping mechanism, and the lower end of the inner tube isusually nested within the outer tube. The inner tube is movable,relative to the outer tube, between a retracted position (in which theseat is relatively closer to the bicycle and most of the inner tube isreceived within the outer tube) and at least one extended position (inwhich the seat is relatively farther from the bicycle and a significantportion of the inner tube is exposed and extended outside the outertube).

To help facilitate the desired extension and retraction of the innertube, dropper seatposts can also include a biasing and locking mechanismthat can be used to urge/bias the inner tube toward at least one of theretracted or extended positions and can also help secure the inner tubein place—such as in its extended position—if the rider wishes to keepthe seat at a given height/position. Preferably, the biasing and lockingmechanism can be arranged to bias the inner tube (and seat mountedthereon) to its extended position, and then maintain the inner tube inthis position until the rider chooses to have the inner tube retracted.In the embodiments described below, the biasing and locking mechanismincludes a locking spring cartridge assembly.

Preferably, the dropper seatposts also include some type of actuatormechanism that a rider can use to actuate/trigger the biasing andlocking mechanism, to allow the rider to selectably alter the seatheight. For example, the dropper seat post can include an actuatorassembly that is used to trigger and/or selectable lock and unlock thelocking spring cartridge assembly. The locking spring cartridgeassembly, as described herein, can be configured so that it remainsfixed/lock when not engage by the actuator assembly, and will stay ineither its extended or retracted position. The locking spring cartridgeassembly is preferably biased toward its extended position, whereby ifthe locking spring cartridge assembly is retracted and is then unlockedby the rider via the actuator, the locking spring cartridge assembly canapply a biasing, extension force that urges the inner tube (and seat)toward its extended position—thereby raising the seat. With the actuatordisengaged, the locking spring cartridge assembly is considered lockedand will resist movement/retraction of the inner tube. That is, thelocking spring cartridge assembly force will resist the axial/verticalloads on the inner tube while in use to help keep the seat at thedesired height, but the resistance of the locking spring cartridgeassembly may be overcome if a sufficiently large axial/vertical force isapplied. Allowing the locking spring cartridge assembly to yield inresponse to an overload situation (e.g. when the applied force passes apredetermined load threshold), while remaining sufficiently rigid whensubjected to loads below the predetermine load/yield threshold may beadvantageous because it can allow the post to support the weight of therider when in use (in a manner that is perceived to be stable by therider), while allowing the post to yield when overloaded to avoiddamaging or bending portions of the post or injuring the rider. Having acushion quotient, Q_(C), which is sufficiently high can help achievethis desired performance.

When a rider wishes to lower the seat height, the actuator is engaged,and the rider can apply a downward force on the seat (typically usingtheir body weight) that is sufficient to overcome the biasing force ofthe locking spring cartridge assembly so that the inner tube can beretracted into the outer tube. Once retracted, the actuator isdisengaged, thereby locking the locking spring cartridge assembly andkeeping the inner tube in its retracted position. In this arrangement,the biasing force of the locking spring cartridge assembly when unlockedis preferably set relatively low so that the inner tube can be retractedusing the body weight of the rider (and of riders of potentiallydifferent sizes and weights), whereas the force required to causemovement of the locking spring cartridge assembly when it is locked isrelatively higher, but below the predetermined threshold.

To make things convenient for the rider, the triggering mechanism/remotefor the actuator assembly can be provided at another location on thebicycle, such as on the handlebars, and can be operatively connected toan actuator assembly by a remote connector (such as a wire, cable,chain, lever, pneumatic or hydraulic link or the like). Because suchremotes are usually connected to the actuator assembly in amechanical/fluid power manner that transmits forces back to the user, itis preferable that the force required to engage the actuator assemblyremains in a range that is feasible/comfortable for the rider to applyusing the remote, and more preferably the force required to engage theactuator assembly remains relatively constant whether the inner tube isextended or retracted. This may help provide a more consistent tactileexperience for the rider.

The inventor has determined that the extension force, overload yieldforce and other parameters of the dropper post can be configured bymodifying aspects of the locking spring cartridge assembly design, suchthat a new dropper post has been created in which the actuation force ofthe spring cartridge assembly device is not materially affected by theinstantaneous load that is being applied to the seat (e.g. can operatein substantially the same way when the seat is loaded or unloaded),and/or where, when the spring cartridge assembly is locked (e.g. thepiston valve is closed), the upper tube can remain sufficiently rigid toresist loading of the seat up to a pre-determined, overload force abovewhich the post can compress slightly to help protect the post fromdamage and/or the rider from injury. Examples of suitable locking springcartridges that can be used in such dropper posts are described herein.

FIGS. 1-5 illustrate one example of a dropper seat post 100 includes aninner tube 110, seat clamps 150 (for connecting to a bicycle seat—notshown), an outer tube 120, a seat collar 130, an actuator assembly 140,including actuator mechanism 170, and a locking spring cartridgeassembly 160. In this arrangement, both the inner tube 110 and outertube 120 are elongate, tubular members that extend along a post axis102. While the post axis 102 is shown as generally vertical in FIGS. 1and 2 , when the dropper post 100 is installed on a bicycle the postaxis may be inclined and need not be vertical.

In this example, the inner tube 110 is configured to slidetelescopically within the outer tube 120 between a retracted position(FIG. 1 ) and an extended position (FIGS. 2 and 4 , for example). Theinner tube 110 includes a lower end 112 that is sized to fit within theouter tube 120 and that is intended to be retained within the outer tube120 in both of the seat post's 100 retracted (FIG. 1 ) and extendedconfigurations (FIG. 2 ). The inner tube 110 also has sidewall with aninner wall surface 111 and defines an inner tube outer diameter (D_(TO))113 and inner tube inner diameter (D_(TI)) 114. While the term innertube diameter is used for convenience in this description, it ispossible in some examples that the inner wall does not have a circularcross-sectional shape, and may have an oval shape, rectangular shape orother suitable shape, even if the outer shape is circular orsubstantially circular. As described herein, the interior of the uppertube is preferably sized to accommodate the associated spring cartridgeassembly (as described herein) and can influence the formula that isused to calculate its moment of inertia (as described herein), but thevalues for the moment of inertia can be compared for different shapes.Therefore, references to inner diameters can be understood to mean innerwidth and/or other relevant interior measurement that is useful forcalculating the moment of inertia for a given shape. The term diameteris not intended to limit the present teachings to only be applicable toposts with a circular interior shape.

Referring to FIGS. 3-5 , one example of a locking spring cartridgeassembly 160 that is suitable for use with the dropper posts describedherein includes a cartridge outer tube 161 that has a sidewall with aninner surface that can be engaged by portions of the cartridge and canform part of the boundary of internal cartridge chambers and/or may bepart of the sealing structures. In this example, the inner surface ofthe cartridge outer tube 161 can be referred to as an inner slidingsurface 191 that defines a sliding surface diameter 191 a. The cartridgeouter tube 161 is preferably connectable to the inner tube 110 in amanner that is sufficiently strong enough to carry the forces describedherein, and that allows the inner tube 110 to move with the cartridgeouter tube 161. In the illustrated example, the cartridge outer tube 161includes upper connection portion 162 for attaching cartridge 160 toupper tube 110, but other fasteners could be used. In addition to thecartridge outer tube 161, the locking spring cartridge assembly 160 alsoincludes a cartridge rod 163 with a cartridge rod diameter 163 a, alocking groove 165 at a lower end 166 of the cartridge rod 163, and anactuation rod 164. Fixedly attached to sliding surface 191 are an upperseal assembly, including the upper seal head 192, and a lower sealassembly, including lower seal head 193, which together help seal in theinterior of the cartridge outer tube 161 and substantially fluidlyisolate the interior of the cartridge outer tube 161 from thesurrounding environment (at least with a sufficient degree ofsealing/isolation to facilitate the operation of the locking springcartridge assembly 160 as described herein).

Within the interior of the cartridge outer tube 161 a piston assembly isprovided to separate the interior of the cartridge outer tube 161 intotwo different chambers, and to help facilitate the translation of thecartridge outer tube 161 as described. The piston assembly can be of anysuitable configuration that can operate as described herein. A valvemechanism is also preferably provided that can selectably allow fluidcommunication between the chambers on opposite sides of the pistonassembly, as this can be used to lock and unlock the locking springcartridge assembly 160. The valve, and related fluid flow path regions,can be of any suitable configuration. To help reduce the overall size ofthe locking spring cartridge assembly 160, it may be preferable tointegrate a suitable valve mechanism within the piston assembly, as isshown in the present example that includes a piston valve 194 attachedto the upper end 163 a of a cartridge rod 163 that can extend from thepiston valve 194 to the actuator assembly 140. The piston valve 194 issized to generally fill the cartridge outer tube 161, is positionedaxially between the upper and lower cartridge seal heads 192 and 193 andhas a sealing portion that is positioned opposite and configured to sealagainst the sliding surface 191 and includes a body-sliding-surfaceo-ring 198 (or other suitable translatable sealing member). The pistonvalve 194, in this example, also includes a valve body 195, a plunger196 that can move relative to the valve body 195, a body-piston o-ring197, and valve cap 199. In this embodiment the valve cap 199 defines avalve cap channel 199 a and the valve body 195 defines a correspondingvalve body channel 195 a and a valve inner pathway 195 b. The plunger196 includes a seal surface 196 a, that can seal against the valve body195 (e.g., against o-ring 197 in this example) to inhibit fluid flowthrough the piston valve, and neck portion 196 b.

In this arrangement, the piston 194 divides the interior of thecartridge outer tube 161 into two operating chambers that can be fluidlyisolated from each other while the locking spring cartridge assembly 160is in use to selectably lock and unlock the locking spring cartridgeassembly 160. For example, when the operating chambers are fluidlyisolated from each other the locking spring cartridge assembly 160 canbe considered to be in a locked configuration and will resist movementof the cartridge outer tube 161 and seat post inner tube 110. Incontrast, when the operating chambers are fluidly connected, such as byactivating the piston valve 194 and allowing fluid (liquid) to passthrough the piston 194 and flow between the operating chambers, thelocking spring cartridge assembly 160 can be considered to be in anunlocked configuration and will facilitate the relative movement of thecartridge outer tube 161 and seat post inner tube 110 relative to theouter tube 120. As described herein, when the locking spring cartridgeassembly 160 is in use, and the piston valve 194 is opened, thecartridge outer tube 161 can translate relative to the piston 194 toallow the seat post inner tube 110 to translate relative to the outertube 120.

Referring to FIGS. 4 and 5 , in this example one, or a first, of theoperating chambers is chamber 181, which is located axially between thepiston valve 194 and the lower seal head 193 and is laterally bounded bythe sliding surface 191. Preferably, the lower chamber 181 is configuredto contain only, or at least substantially only liquid, such as the oildescribed herein, rather than a mixture of liquid and gas or othermaterial and can also be referred to as a liquid chamber. When thelocking spring cartridge assembly 160 is in use within the seat post 100in the orientation illustrated these Figures (which is also theorientation of the locking spring cartridge assembly 160 when it is inuse on a bicycle) the chamber 181 can be referred to as a lower chamber181, but it is understood that the term lower is used for convenienceand is not intended to limit the orientation of the locking springcartridge assembly 160 when in use.

In the present example, the other, or second, operating chamber ischamber 182 which is located axially between the piston valve 194 andthe upper seal head 192 and is also laterally bounded by the slidingsurface 191. Because of its relative location within the locking springcartridge assembly 160 as illustrated, the second chamber 182 can bereferred to as an upper chamber 182, but it is understood that the termlower is used for convenience and is not intended to limit theorientation of the locking spring cartridge assembly 160 when in use. Incontrast to lower chamber 181, the upper chamber 182 is preferablyconfigured to contain a mixture of oil (or other suitable liquid) andpressurized air (or other suitable gas), instead of containing onlyoil/liquid, and can be referred to as a gas/liquid chamber.

Under the intended operating conditions of the locking spring cartridgeassembly 160 the oil and air (or other liquid and gas) in the gas/liquidchamber 182 with tend to separate from each other due to the differencesin their densities and mechanical properties, such that an air/oilinterface or boundary 183 is defined between piston valve 194 and upperseal head 192 within chamber 182. In this arrangement, the gas/liquidchamber 182 will have a lower layer or region containing oil occupyingthe space located axially between the boundary 183 and the piston valve194, and an upper layer or region that is above the oil layer andboundary 183 and is located axially between the boundary 183 and theupper seal head 192. When the piston valve 194 is actuated and its valveis open, fluid communication between the liquid layer within chamber 182and the liquid within the lower chamber 181 is established.

While illustrated as separate members in this example of dropper seatpost 100, the cartridge outer tube 161 and upper tube 110 mayalternatively be integrally formed with each other and as is shown inanother example of a dropper seat post 200. The seat post 200 isanalogous to seat post 100 and like features are illustrated using likereference characters indexed by 100. As described further herein, seatpost 200 can operate in substantially the same manner as seat post 100but may have some slightly different components and configurations as aresult of the integral formation of the cartridge outer tube 161 andupper tube 110 that do not materially alter how the posts 100 and 200operate. For example, if the cartridge outer tube 161 and upper tube 110are of integral, one-piece construction as shown in this second examplethen features such as the upper connection portion 162, that is used toconnect the separate cartridge outer tube 161 to the upper tube 110 inthe previous example, is not needed. Similar functioning components ondropper post 100 will now be described using characters indexed by 100(i.e., 163 is now 263).

FIGS. 6-7 illustrate an example of a dropper seat post 200 that embodiesanother preferred embodiment of the teachings described herein. In thisexample, the seat post 200 includes an inner tube 210, seat clamps 250,outer tube 220, seat collar 230, actuator assembly 240, includingactuator mechanism 270. The inner tube 210 further includes lower end212, inner wall surface 211, inner tube outer diameter (DTO) 213 andinner tube inner diameter (DTI) 214.

In contrast to the seat post 100, in this example the inner tube 210 andouter cartridge tube 261 are integrally formed together (i.e., are ofintegral, one-piece construction) so that the inner tube 210 forms apart of locking spring cartridge assembly 260. This example of thelocking spring cartridge assembly 260 further includes an inner slidingsurface 291 that defines a respective sliding surface diameter 291 a(which is the same as tube inner diameter 214 in the case of dropperpost 200), cartridge rod 263 defining a cartridge rod diameter 263 b,locking groove 265 and actuation rod 264. Fixedly attached to slidingsurface 291 are upper seal head 292 and lower seal head 293. While fixedduring the operation of the locking spring cartridge assembly 260 tohelp contain the liquid and gas within the cartridge tube 261, the upperand lower seal heads 292 and 293 (and analogous seals 192 and 193) canbe removed for maintenance, assembly of the mechanism and for any otherreason while the seat post 200 (or 100) is not in use.

In this example, the piston valve 294 is attached to the upper end 263 aof cartridge rod 263 and is positioned so that it can seal against andslide relative to the sliding surface 291 and is located axially betweenthe upper and lower cartridge seal heads 292 and 293. In this example,the sliding surface 291 is an inner surface of the inner tube 210.

Piston valve 294 further contains a valve body 295, a plunger 296, abody-piston o-ring 297, body-sliding-surface o-ring 298 (or othersuitable sealing member) and valve cap 299. In this example, the valve(including the valve body 295, plunger 296 and related sealing members,etc.) are included as part of the piston that separates the chambers 281and 282, which can help reduce the overall size of the dropper post 200.Alternatively, a different type of valve and liquid flow path may beprovided that does not necessarily require the flow path to extendthrough the piston as illustrated.

Valve cap 299 defines a valve cap channel 299 a and valve body 295defines a valve body channel 295 a and a valve inner pathway 295 b.Plunger 296 further defines seal surface 296 a and neck 296 b. Lowerchamber 281 located within sliding surface 291 and between piston valve294 and lower seal head 293 contains only oil (or other suitableliquid). Upper chamber 282 that is bounded by the sliding surface 291and located axially between piston valve 294 and upper seal head 292preferably contains a mixture of oil (or other suitable liquid) andpressurized air (or other suitable gas). When dropper post 200 is in asubstantially upright position (as illustrated in FIGS. 6 and 7 ), theoil and air in chamber 282 will tend to separate from each other, withthe oil occupying the lower portion of the space adjacent piston valve294 and the relatively less dense air occupying the upper portion of thechamber 282 space adjacent the upper seal head 292. An air/oil boundary283 is therefore defined between piston valve 294 and upper seal head292 within chamber 282.

FIGS. 8-9 show the actuator 240, and lockable spring cartridge assembly260 in use. While the operation of the actuator and cartridge isdescribed with reference to the actuator 240, and lockable springcartridge assembly 260, actuator 140 and lockable spring cartridgeassembly 160 have substantially the same features and are operable in ananalogous manner (regardless of whether the cartridge outer tube is aseparate member or is integrally formed with the dropper post innertube). Further, while a given actuator 240 is described for convenience,other suitable actuators may be used provided that they can selectablytrigger the piston valve 294 (or 194) to enable the locking andunlocking of the spring cartridge assembly.

In the illustrated examples, actuator 240 includes a body 243, acartridge rod receiving portion 247 for attaching cartridge rod 263 tobody 243, an inner tube stop surface 246 and an actuation mechanism 270to push actuation rod 264. Upper tube stop surface 246 may exist on body243 or as illustrated may be the upper surface of cushioning member 244.

Cartridge rod 263 can be attached to rod receiving portion 247 ofactuator body 243 in any suitable manner. In the illustrated examplebolts 245 a and 245 b are provided and interact with locking groove 265to securely connect the cartridge rod 263 to the actuator body 243.Alternatively, other suitable methods such as threaded engagement, apress-fit, a deformation fit, or the like could be used.

Actuator body 243 of actuator 240 can be attached to lower tube 220using any suitable techniques or fasteners, and preferably may beremovable connected to allow access to the interior of the lower tube220. In the illustrated example, body 243 uses circlip 241 that engageswith groove 221 of lower tube 220. Other suitable methods such asthreads, a press-fit, a deformation fit, or the like could be used.

To operate the piston valve 294, the actuator 240 can also include asuitable actuator mechanism 270, which in this example includes a lowerarm 271 that has a dynamic cable stop surface 277. An upper arm 272 islinked to the lower arm 217 and includes an actuation rod contactsurface 278 that is configured to engage the lower end of the actuationrod 264. Pivot pins 273 and 274 are used to connect the lower and upperarms 271 and 272 to each other and to the body 243 and to facilitate thedesired pivoting of the arms 271 and 272 when the actuator 240 is inuse. An alignment pin 275 is used to help guide the movement of theupper arm 272, and preferably to limit movement of the upper arm 272 toa substantially axial translation as the pin 275 is captive, and slideswithin a corresponding slot in the upper arm 272.

In this example, the actuator mechanism 270 uses a cable and housingarrangement (not shown—but that can be connected to a suitable remotetrigger unit) to lower the distance between static cable stop surface242 of body 243 and dynamic cable stop surface 277 of lower arm 271 whentension is applied to the cable (i.e. to pull the cable stop surface 277downwardly as illustrated in FIG. 8 ). Lowering the distance betweencable stops 277 and 242 pivots lower arm 271 about pin 273 therebypushing upper arm 272 upward while it pivots about pin 274. Upper arm272 is aligned to body 243 by alignment pin 275.

When the lower arm 271 is pivoted in this manner in response to tensionbeing applied on the actuating cable, the upper arm 272 moves upwardlyand the actuation rod contact surface 278 pushes actuation rod 264upward (as illustrated0). Axial movement of the actuation rod 264 thencauses a corresponding axial movement of the translating plunger 296(upwardly as illustrated) thereby ‘opening’ the piston valve 294. FIG. 8shows actuator assembly 240 in a relaxed (closed) position. FIG. 9 showsactuator mechanism 240 in an actuated (open) position. Because plunger296 translates into the upper chamber 282 containing gas and oil, thegas can compress as the plunger 296 moves into the upper chamber 282therefore the force required to move plunger 296 is less than it wouldbe if attempting to translate into chamber that contained oil/liquid.This arrangement can help facilitate the actuating of the piston valve294, via the translation of plunger 296, with a substantially constantamount of force being required regardless of the axial position and/orrelative loading of the inner tube 210 (or 110), e.g. where a plungingforce required to translate the plunger 296 when the inner tube 210 issubjected to an axial load is within about 20%, and preferably withinabout 10% or 5% of the force required to translate the plunger 296 whenthe inner tube 210 is loaded (whether measured as tension on the cable,axial force acting on the actuator rod 264, feedback experienced by arider at the remote triggering unit, or the like).

Once actuated (opened) plunger 296 translates upward and seal surface296 a of plunger 296 unseats from o-ring 297 and the neck 296 b issufficiently smaller in diameter that it does not seal against o-ring297. In this example, when the plunger 296 is translated in this way afluid flow path (including channel 299 a, pathway 295 b and channel 295a) is established within the piston valve 294 and between the chambers281 and 282, and they are in fluid communication with each other. Thatis, oil from chamber 282 can travel through channel 299 a, pathway 295 band channel 295 a into chamber 281, and vice versa. As such when thepiston valve 294 is actuated (open) relative axial movement is possiblebetween cartridge rod 263 and inner tube 210. Relative axial movementbetween upper tube 210 and lower tube 220 is therefore also possible.

When cartridge 260 is actuated (opened), and inner tube 210 is urgedtowards its retracted position, it can reach a lower limit in outer tube220 when upper tube lower surface 212 contacts upper tube stop surface246. The travel or drop length of the post is then defined, in thisexample, by the distance 248 between lower end 212 of the inner tube 210when it is in its extended position (FIG. 8 ) and the upper tube stop246. The drop length is preferably long enough to allow the seat to bein a comfortable riding position when the dropper post is extended, andto be sufficiently lowered so as to not substantially interfere with therider when the dropper post is retracted. In some examples, the droplength 248 can be at least 190 mm, 195 mm, 200 mm, 205 mm, 210 mm, 215mm, 220 mm, 225 mm, 230 mm, 235 mm, 240 mm, 245 mm or more, andpreferably may be between about 190 mm and about 230 mm, or betweenabout 200 mm and about 225 mm.

If valve 294 remains open and the force urging tube 210 towards itsretracted position ceases (e.g., if the rider is not sitting on the seator otherwise pushing to try and retract the inner tube 210), then thelocking spring cartridge assembly 260 in this example will bias theinner tube 210 to extend with an extension force F_(E). In theillustrated configuration, the extension force F_(E) is defined by theproduct of the air pressure P in chamber 182 and the cross-sectionalarea of rod diameter (D_(R)) 263 b as shown in the following equation.

$F_{E} = {P \times {\pi\left( \frac{D_{R}}{2} \right)}^{2}}$

The inventor has determined that configuring the air within the secondchamber 282 to be at a predetermined, operating pressure, can helpdictate the magnitude of the extension force F_(E) for a given springcartridge assembly geometry, which can in turn help determine theperceived stiffness of the dropper post and the yield force as describedherein. The operating pressure can be varied based on the specificgeometry of a given dropper post to help obtain the desired performance,but in the illustrated example can be about 300 psi, and in otherexamples may be equal or less than 300 psi, such as between 200 psi and300 psi, and preferably between about 250 psi and about 300 psi. Inother examples, the operating pressure and relevant diameters (e.g., 291a/214 and 263 b) can be selected for a given arrangement so that theextension force F_(E) and other relevant forces and ratios describedherein fall within the desired ranges.

One example of a suitable operating pressure P for the gas withinchamber 282 that can be used for exemplary description purposes is anoperating pressure of about 300 psi, and one example of a suitable D_(R)would be 8 mm (0.315″) Therefore the F_(E) calculation would be asfollows:

$F_{E} = {300 \times {\pi\left( \frac{0.315}{2} \right)}^{2}}$F_(E) = 23.37lbs

The inventor has discovered that the extension force F_(E) under theseconditions is sufficient to overcome the anticipated friction betweeninner tube 210 and outer tube 220 while the inner tube 210 is movedtoward its extended position but is also low enough to allow the rider'sbody weight to overcome in order to urge inner tube 210 toward aretracted position while piston valve 294 is open. Preferably, theinventor has determined that the extension force F_(E) should be betweenabout 15 and 35 lbs and preferably may be between about 20 and 25 lbs.As noted herein, the parameters of any given spring cartridge assemblycan be selected so that the resulting extension force F_(E) is withinthis desired range.

Referring also to FIGS. 10 and 11 , the dropper post 200 is shown withits piston valve 294 in its open configuration, as it would be when arider has triggered the actuator 240. With the dropper post 200 In thisconfiguration, if the rider wishes to move the inner tube 210 to itsretracted position (FIG. 11 ) the axial force applied to the inner tube210 must exceed the extension force F_(E) (and any friction forces andlosses, which are considered to be negligible as compared to the mainextension force). Once extension force F_(E) threshold has been exceededthe inner tube 210 will proceed to translate towards a retractedposition while oil is transferred from upper chamber 282 to lowerchamber 281. FIG. 11 shows dropper post 200 in a fully retractedposition.

FIGS. 12 and 13 show actuation mechanism 270 in its relaxed (closed)position and with the piston valve 294 in its closed position. In thisarrangement, the fluid path between the upper chamber 282 and the lowerchamber 281 is interrupted and the spring cartridge assembly 260 can beconsidered to be locked. When in this state, a force used to urge innertube 210 towards a retracted position will place the oil in lowerchamber 281 in tension, as moving the inner tube 210 downwardly relativeto the piston valve 294 would lead to an to increase the volume of lowerchamber 281, which would tend to lower the pressure acting on the liquidwithin the chamber 281. The generally incompressible nature of theliquid in the lower chamber 281 will tend to resist such movement whilethe piston valve 294 is closed. The combination of the liquid and gas inthe upper chamber 282 may also tend to resist such relative movement ofthe piston valve 294 into the upper chamber 282 and compression of theinterior of the upper chamber 282. However, because the gas in the upperchamber 282 is relatively compressible, the resistance to the movementof the piston valve 294 provided by the upper chamber 282 may be lessthan the resistance provided by the lower chamber 281.

In this arrangement (e.g., while the piston valve is closed and thespring cartridge assembly is locked) the inner tube 210 will remainsubstantially, axially fixed relative to outer tube 220 (and pistonvalve 294) until a sufficient force is applied to overcome the tensile,resistive force that is generated by the oil under tension in lowerchamber 281. That is, the spring cartridge assembly will provide aresistive force that opposes axial movement of the inner tube when thespring cartridge assembly is locked, and in particular a resistive forcethat will oppose the retraction of the inner tube 210 (e.g., will opposemovement of the inner tube 210 toward the retracted position). If asufficiently large force is applied to the inner tube 210 that themagnitude of the applied force exceeds the resistive force of thecartridge, then relative motion between the piston 294 and the cylindercan occur, which will then result in an expansion of the volume of thechamber 281 which in turn lowers the vapour pressure within the chamber281 and can pull dissolved gas(es) out of solution from the oil withinchamber 281. This resistance force that opposes axial movement of theinner tube when the spring cartridge assembly is locked can be referredto as a degassing force (F_(D)), and a force that exceeds the degassingforce can be referred to as an overload force. The inventor hasdetermined that the degassing force should preferably be between about80 and 160 lbs and preferably between about 90 lbs and 140 lbs orbetween 90 and 120 lbs, and more preferably is less than 100 lbs, and isbetween 90 and 100 lbs. This range of forces has been found to offer asatisfactory rider experience and seat feel, while also allowing theseat post to yield when subjected to the overload forces as describedherein. The inventor has also determined that this degassing force(F_(D)) can be a function of the geometry of the spring cartridgeassembly 260 and can be expressed as a force multiplier (M_(F)) ofextension force (F_(E)) of a given cartridge, according to the relationbelow:F _(D) =M _(F) ×F _(E)

To obtain a desired balance of extension and degassing forces in acommercial dropper post, the inventor has determined that the desiredfor force multiplier M_(F) value may be between 3 and 6 and maypreferably be between 4 and 5.

Using these novel parameters, if, in one example, a low-end of extensionforce F_(E) range may be about 15 lbs, which if multiplied by an M_(F)of 6 could result in a force F_(D) of about 90 lbs. If the cartridge isdesigned so that the extension force F_(E) is toward the higher end ofpreferred range and is about 35 lbs, which if multiplied by an M_(F) of3 this would result in a degassing force F_(D) of about 105 lbs.

When developing the present inventions, the inventor further determinedthat the force multiplier (M_(F)) is also proportional to the quotientof sliding surface diameter (D_(S)) 291 a of the spring cartridgeassembly upper tube 261 and rod diameter (D_(R)) 263 b. That is:

$M_{F} \propto \left( \frac{D_{s}}{D_{R}} \right)$

Preferably, when constructing dropper posts in accordance with thepresent teachings, the sliding surface diameter D_(S) may be betweenabout 18 and 25 mm and preferably between about 20 and about 23 mm, asthis may help provide a dropper post of a reasonable size that may fitmany standard bicycles. The inventor has determined that acceptable roddiameters D_(R), e.g., that provide a suitable level of strength whilestill fitting into the other size limitations and area ratios that areused to provide the desired performance of the dropper posts describedherein, may optionally be between about 6 and 10 mm and preferablybetween about 7 mm and about 9 mm.

As one of the factors that can be balanced in a given dropper postembodiment, the ratios of sliding surface diameter D_(S) to rod diameterD_(R) may therefore be between about 1.8 (18 divided by 10 or 18/10) and4.17 (25 divided by 6 or 25/6), between about 2.22 (20 divided by 9 or20/9) and about 3.29 (23 divided by 7 or 27/3) and preferably about2.625 (21 divided by 8).

Based on one known experimental data set that was obtained from apublication entitled Lockable Gas Springs “Gas Top” produced in 2021 byVapsint® Gas Springs and Dampers, and available at, the force multiplier(M_(F)) versus the quotient of sliding surface diameter (D_(S)) 291 aand rod diameter (D_(R)) 263 b can be expressed as graph of M_(F) vs(D_(S)/D_(R)) as shown in FIG. 15 .

One way of determining the force multiplier M_(F) can be further definedbased a line of best fit from the graph in FIG. 15 as:

$M_{F} = {{{3.7}2\left( \frac{D_{s}}{D_{R}} \right)} - {{5.5}9}}$

While fitting different lines of best fit may produce slightly differentslope and y-intercept values, the inventor has determined that thepreferred spring cartridge assembly performance can be obtained usingvalues that are not materially different than those provided herein.That is, the M_(F) for a given example may be within about 10% of thevalue of the line of best fit equation.

One exemplary calculation for force multiplier M_(F) using thisexperimental line of best fit and a ratio of sliding surface diameterD_(S) to rod diameter D_(R) of 2.625 (from above) is:

M_(F) = 3.72(2.625) − 5.59 M_(F) = 9.77 − 5.59 M_(F) = 4.18

While allowing for some variation in the constants in this exampleequation, the M_(F) that is within about 10% of this calculated valuemay be between about 3.76 and about 4.6. Given these exemplary ratiosabove of sliding surface diameter D_(S) to rod diameter D_(R), forcemultiplier M_(F) may be calculated as being between about 1.11(D_(S)/D_(R)=1.8) and 9.91 (D_(S)/D_(R)=4.17), between about 2.67(D_(S)/D_(R)=2.22) and about 6.65 (D_(S)/D_(R)=3.29) and preferablyabout 4.18 (D_(S)/D_(R)=2.625). Based on this, the preferred forcemultipliers M_(F) may be between 3 and 6 and may preferably be between 4and 5.

In these illustrated examples, if, while the piston valve 294 is closedand the spring cartridge assembly is considered to be locked, inner tube210 is urged towards its retracted position with a force that less thandegassing Force F_(D), inner tube 210 will remain axially fixed withouter tube 220. This can help facilitate the desired rider experienceand the desired feeling of solidity and stability of the dropper post.However, when the force urging the inner tube 210 toward its retractedposition exceeds the degassing force F_(D) (and any associated losses,friction forces and the like), dissolved air is pulled out of solutionwithin lower chamber 281. Small air bubbles 285 form in lower chamber281 and this can allow a relatively small amount of relative axialmovement of the inner tube 210 relative to the piston valve 294, shownas the overload cushion distance 284 (as shown in FIGS. 12 and 13 ).Preferably, the overload cushion distance 284 is less than the expecteddrop length 248 of the dropper post 200, and more preferably may be atleast, and optionally can be between about 1 mm and 40 mm or between 10mm and about 30 mm and can between about 0% and about 20% of the travellength 248, and preferably can be between about 5% and about 15% of thetravel length 248 to help provide a desired deflection or cushioning.This axial movement 284 therefore acts as a cushion if a rider overloadsthe post, such as while when riding or during a crash. Once the forceurging inner tube 210 toward the retracted position drops back below thedegassing force F_(D), the air bubbles 285 can go back into solution andthe inner tube 210 returns to its original height (FIG. 12 ).

FIG. 12 further shows the location of a plane A, illustrated when theinner tube 210 of dropper post 200 is in its extended position. Theplane A in this arrangement is at a location that is located along thelength of the inner tube 210 and is adjacent the upper end of outer tube220 and seat collar 230. The moment of inertia at plane A relates to thestrength of inner tube 210 for a given material and load. This location,adjacent the seat collar 230 is a location where the inner tube 210 maybe subjected to relatively high bending loads, as the portions of theinner tube 210 that are below the seat collar 230 are nested in andsupported by the outer tube 220, while portions of the inner tube 210that are exposed above the seat collar 230 are not supported in the samemanner. Providing an inner tube 210 that is sufficiently strong at thislocation can help resist bending of the inner tube 210 when in use andextended.

In addition to conforming with the multiple geometric parametersdescribed herein to provide the desired spring cartridge assemblyparameters, the moment of Inertia Ix for inner tube 210 at Plane A isdefined by tube outer diameter D_(TO) and tube inner diameter D_(TI) asfollows:

$I_{x} = \frac{\pi\left( {D_{TO}^{4} - D_{TI}^{4}} \right)}{64}$

To help the dropper post 200 fit with standard bicycle tubes, the innertube outer diameter D_(TO) may be 25.5-30 mm and preferably is about26-28 mm. The ratio of tube inner diameter D_(TI) to tube outer diameterD_(TO) may preferably be less than about 82.5% and preferable less thanabout 80%.

For example, the moment of inertia Ix for one preferred embodiment wouldhave a diameter D_(TO) of about 26 mm and a diameter D_(TI) of about20.8 mm (80% of diameter D_(TO)). The resulting moment of inertiacalculation would be as follows:

$I_{x} = \frac{\pi\left( {{26^{4}} - {2{0.8^{4}}}} \right)}{64}$$I_{x} = \frac{\pi(269,798.6)}{64}$ I_(x) = n(4415.6)I_(x) = 13, 243.7mm⁴

Similarly, the inventor has discovered that the moment of inertia Ix forthe preferred ranges of tube outer diameters DTO and tube innerdiameters DTI described herein may be between about 11,140 mm⁴(DTO=25.5, DTI=21.0 (82.5% of diameter DTO)) and about 23,474 mm⁴(DTO=30, DTI=24.0 (80% of diameter DTO)).

FIG. 14 shows the cross section of inner tube 210 taken at Plane A ofthe illustrated embodiment and includes an inner tube outer diameter(DTO) 213 and inner tube inner diameter (DTI) 214 as two co-axialdiameters. While in these examples the tubes 210 and 220 are shown asbeing circular in cross-sectional shape, other shapes and be usedincluding ovular, non-coaxial circles or various sided polygons and themoment of inertia calculation would change to another known formula, butanalogous ratios could be utilized.

Using the preferred geometries of the tubes 110 and 210 that can helpprovide the desired areas and forces described herein, the inventor hasdiscovered that the moment of inertia at plane A for such designs may begreater than about 11,000 mm⁴, and in some more preferred examples canbe greater than about 13,000 mm⁴. Similarly, the tube outer diameterD_(TO) may be 25.5-30 mm and preferably 26-28 mm, and therefore theratio of tube inner diameter D_(TI) to tube outer diameter D_(TO) may beless than about 82.5% and preferable less than about 80%, and the ratioof Ix of inner tube 210 (in mm⁴) at plane A to the force multiplierM_(F) (Ix/M_(F)) may define a ratio described herein as the cushionquotient Q_(C), and the inventor has determined that preferred examplesof the dropper posts described herein can have a cushion quotient thatis equal to or greater than about 2400 mm⁴, 2500 mm⁴, 2600 mm⁴, 2700 mm⁴or more. The table below shows moment of inertia, force multiplier andcushion quotient values for two examples dropper posts considered by theinventor.

Ix at Cushion Operating Plane Quotient D_(TI) D_(TO) D_(S) D_(R) Ds/pressure F_(E) F_(D) A Ix/M_(F) Post (mm) (mm) (mm) (mm) Dr M_(F) (psi)(lbs) (lbs) (mm⁴) (mm⁴) 1 26 20.8 20.8 8 2.6 4.082 300 23.37 95.4113243.70 3244.41 2 28 24 24 8 3 5.57 300 23.37 130.19 13885.83 2492.96

As described herein, dropper seat posts usually consist of an inner(upper) tube and an outer (lower) tube that selectively move relative toeach other is a telescoping fashion. This allows the rider to change theheight of their seat without having to stop and adjust a mechanicallytightened seat post collar. It is advantageous to lower the bicycle seatas far as possible when riding through technical terrain to allow therider to change body position or bend their knees deeply withoutcontacting the seat.

Modern dropper post locking spring cartridge assemblies are typicallyconfigured with two or more chambers containing liquid (i.e., hydraulicoil), gas (i.e., air) or a combination thereof. There is typically aninternal piston valve controlled by an actuator/remote and an actuationrod translatable between an open and a closed position. When the pistonvalve is closed and a rider sits on a seat attached to the top of thepost, the chamber containing, by design, only oil is placed incompression thereby allowing the post to be loaded without retracting.

A locking spring cartridge assembly typically consists of at least acartridge outer tube and a cartridge rod. In some configurations thecartridge outer tube may be fixedly attached to the upper end of theseatpost inner tube by some form of suitable fastener. The cartridge rodmay also be fixedly attached to the lower end of the seatpost lower tubeand/or to the actuator body. When a valve inside the locking springcartridge assembly is opened the cartridge outer tube can translaterelative to the cartridge rod in a telescoping fashion. In thisconfiguration the cartridge outer tube moves with the seatpost innertube, and the cartridge rod moves with the seatpost outer tube. When thecartridge valve is selectively closed relative movement between theseatpost inner and outer tube ceases to be possible.

Dropper seatposts are typically sold in multiple drop lengths within agiven model of a given manufacturer. For example, OneUp Components sellsa “Dropper post V2” product in drop lengths on 90 mm, 120 mm, 150 mm,180 mm, 210 mm, 240 mm. Because the outer diameter of known cartridgesis the same for all drop lengths the inner diameter of the inner posttube is also the same because it is usually sized to fit/accommodate thespecific cartridge outer diameter. The outer sizes/diameters ofcomponents of a dropper seatpost are also usually constrained by otherpractical factors, such as having to fit within the relatively standardsized tubes on a bicycle frame. Therefore, the inner post tubes onconventional dropper seat posts typically have the same inner post tubediameters and wall thicknesses for different drop lengths.

However, the drop length is also correlated to the bending stress theinner tube is exposed to during riding, as described in more detailherein, with relatively longer inner tubes that can provide relativelylonger drop lengths being subjected to relatively larger bendingstresses when in the raised configuration, as compared to a shorter tubehaving a shorter drop length. Due to the practices described above wherelong and short inner post tubes are formed with the same diameters andwall thicknesses, the inner post tubes for a given manufacturer that areintended to be used with a given spring cartridge assembly areconventionally designed to be able handle the highest expectedloads—i.e. the situation that would be faced by a long inner posttube—even if the inner post tube in a specific dropper post assembly isa shorter post with a shorter travel length. This means that relativelyshorter inner tubes that are to be used on relatively shorter dropperposts can have thicker sidewalls and are manufactured with more material(and therefore have a higher weight) than would be required to onlysupport the expected bending forces on a short inner post tube due tothe relatively higher bending strength requirements and extramaterial/wall thickness needs of the longer inner post tubes sized tofit the same spring cartridge design.

FIG. 16 is a cross-sectional view of one example of a dropper post 900having an outer tube 920, collar 930 and an inner tube 910 in which aspring cartridge 960 is mounted in a manner that is known in the priorart shows an example of prior art. In this configuration, threadedprotrusion 964 of the upper end 965 of cartridge 960 extends throughaperture 911 of seat post inner tube 910. Nut 963 may be used tointerface with threaded protrusion 964 of the upper end 965 of cartridge960. Cartridge upper end 965 is thereby pulled into contact with flange912 of tube 910. Groove 962 of rod 961 interfaces with fasteners 941 aand 941 b to fixedly attach rod 961 to actuator 940.

In this illustrated example the cartridge outer tube 967 and rod 961 arenot rotationally fixed to each other about their respective,longitudinal axes (the vertical direction as illustrated in FIG. 16 ).Cartridge upper tube 967 and threaded protrusion 964 that are part ofthe cartridge 960 may tend to rotate relative to the inner tube 910,including when trying to tighten or loosen the nut 963. With otherportions of the cartridge 960, including specifically the cartridgeouter tube 967, being generally inaccessible to the user during thisprocess it can be quite difficult to tighten or loosen the nut 963because a user cannot easily hold the cartridge outer tube 967 in afixed position (i.e. it will tend to rotate with the nut 963), even ifthe user were to hold rod 961 because rotation of the rod 961 relativeto the cartridge outer tube 967 is possible.

Also, in this illustrated example it is very difficult, if notimpossible to access the nut 963 with appropriate tools or the hands ofa user when the seat clamps 950 (and a seat thereon) are installed asshown in FIG. 16 . Accordingly, in this illustrated example the nut 963can only be practically accessed by removing seat clamps 950.

In this illustrated example the lower end 966 of cartridge outer tube967 is not constrained or fixed relative to the inner surface of theinner tube 910. As such, if the inner diameter of inner tube 910 and theouter diameter of cartridge upper tube 967 are not selected to besubstantially the same size there can be an increased risk of cartridge960 buckling or rattling within inner tube 910 while the seat post 900is in use. This condition may lead to the seatpost inner tube 930,cartridge outer tube 967 or both needing to be designed to be heavierthan required in order to reduce the gap between their respectivediameters as described herein.

Referring to FIGS. 17-30 , another example of a dropper post assembly300 for supporting a bicycle seat (not shown) is illustrated. Manyaspects of the seat or dropper post assembly 300 are analogous to thedropper post assembly 100 and like features are illustrated using likereference characters indexed by 200. Notably, the design of the lockingspring cartridge assembly 360 differs somewhat from the design of thelocking spring cartridge assembly 160 and the manner that the lockingspring cartridge assembly 360 is connected to the rest of the assembly(notably the inner post tube 310) is different than in other embodimentsdescribed herein. Portions of the inner post tube 310 are accordinglydifferent than portions of the inner post tube 110 with regards to howthe cartridge 360 engages the inner post tube 310, but the inner posttube 310 can otherwise operate in a manner that is analogous to theinner post tube 110. However, the internal operation of the cartridge360 can be analogous to the operation of cartridge 160 and is consistentwith the descriptions herein. In addition to the differences in theattachment features of the cartridge 360, the dropper post assembly 300can operate in substantially the same manner as seat post 100 but mayhave some slightly different components and configurations as a resultof the design of cartridge 360 or other factors that do not materiallyalter how the posts 100 and 300 operate. Similar functioning componentson dropper post assembly 300 will now be described using charactersindexed by 200 (i.e., 110 is now 310).

In this example, the dropper seat post assembly 300 includes an innertube 310, seat clamps 350 disposed at an upper end of the inner tube 310for connecting to a bicycle seat (not shown), an outer tube 320, a seatcollar 330, an actuator assembly 340, including actuator mechanism 370,and a locking spring cartridge assembly 360.

Referring to FIGS. 19-24 , in this example the locking spring cartridgeassembly 360 that is suitable for use with the dropper posts describedherein includes a cartridge outer tube 361 that has a sidewall with aninner surface that can be engaged by portions of the cartridge and canform part of the boundary of internal cartridge chambers and/or may bepart of the sealing structures. The locking spring cartridge assembly360 also includes a cartridge rod 363, locking groove 365 and compatibleactuator rod 364

In this example, the inner surface of the cartridge outer tube 361 canbe referred to as an inner sliding surface 391 that defines a slidingsurface diameter 391 a. The outer surface of the cartridge outer tube361 defines a cartridge outer diameter 400, which in the illustratedexample is substantially constant along the axial length of thecartridge outer tube 361 (but which could vary along its length in otherexamples).

The cartridge outer tube 361 also includes an upper end wall with anupper cap surface 402 that covers and optionally seals an upper end ofthe cartridge outer tube 361 and that does not need to include the upperconnection portion (such as portion 162 described herein) because theconnection between the outer cartridge tube 361 and the inner post tube310 is different in this example. That is, the upper cap surface 402 canbe any desired configuration, including a substantially flat, planarsurface as illustrated in this example. The upper cap surface 402 couldalso have other configurations, including non-planar configurations,which are desirable to interface with a given inner post tube 310, butpreferably the upper end 404 of the outer cartridge tube 361 does notinclude a fastening mechanism for connecting the cartridge to the innertube 310. Preferably, this means that the upper end 404 of the cartridgetube 361 does not include a fastening mechanism that is configured toengage the inner tube in a manner that would restrain axial movement ofthe cartridge relative to the inner tube, even in arrangements wherethere is some physical engagement between the upper end of the upper end404 of the cartridge tube 361 and the inner post tube 310 and/or wherethe inner post tube 310 provides at least some lateral/radial restrainton the cartridge tube 361. Providing an upper end 404, including uppercap surface 402, that is substantially flat as illustrated may helpreduce the overall axial length of the cartridge outer tube 361. In thisexample, the upper cap surface 402 forms the axially upper most or outermost portion of the cartridge outer tube 361 (and of the entirecartridge 360) and is configured such that is disposed within theinterior of the inner post tube 310 and does not extend axially beyondthe upper end of the inner post tube 310 and need not be accessible fromthe upper end of the inner post tube 310. This may help reduce theoverall length of the cartridge 360 and may help simplify constructionof the cartridge post tube 361 or inner post tube 310. In thisarrangement, the entirety of the cartridge post tube 361, and of thelocking spring cartridge assembly 360 is located axially below andinboard the upper end 317, and the inward facing surface of the upperend wall 319 of the post inner tube 310. The upper end of the post innertube 310 may optionally include a recess 321 (FIG. 33 ) that connects toits interior or may be a solid upper wall that covers and seals theupper end 317 of the post inner tube 310.

The cartridge outer tube 361 is preferably connectable to the inner tube310 in a manner that is sufficiently strong enough to carry the forcesdescribed herein, and that allows the inner tube 310 to move with thecartridge outer tube 361. In the illustrated example, instead of anupper connection portion (such as upper connection portion 162) that isconfigured to attach the cartridge 360 to an upper end of the post innertube 310, the dropper post assembly 300 is configured such that theconnection between the outer cartridge tube 361 and the inner post tube310 is provided toward the lower end 406 of the outer cartridge tube 361and toward the lower end of the inner post tube 310 as described herein.That is, in this example the inner post tube 310 includes a suitabletube engagement member that is configured to engage, and preferablyremovably or releasably engage with a complimentary second orcartridge-related engagement member. When the tube engagement member andsecond engagement member are engaged with each other, then the cartridgeouter tube 361 is fixed relative to, and movable axially along with, theinner post tube 310, and when the tube engagement member and secondengagement member are disengaged from each other, then the cartridgeouter tube 361 is movable relative to, and preferably axially removablefrom, the inner post tube 310.

The tube engagement member can be any suitable structure and optionallybe integrally formed with the post inner tube 310 or may be provided asa separate member that can be connected to the post inner tube 310. Inthis example, referring to FIGS. 20 and 22 , the tube engagement memberincludes threads 408 that are formed in the inner surface of the postinner tube 310, at its lower or inner end 312. Other structures arepossible.

The second or cartridge related engagement member can be any structurethat is compatible with the corresponding tube engagement member, suchas threads that can engage the tube threads 408. Optionally, as shown inthis example, the dropper post assembly 300 can include a separatefastening member that is configured to include an appropriate second orcartridge related engagement member and that can be fastened andunfastened to secure or release the spring cartridge assembly 360relative to the post inner tube 310. Providing the second engagementmember on a separate fasting member, instead of having it integrallyformed on the cartridge outer tube 361 for example, may help simply theconstruction of the cartridge 360 and may allow the walls of thecartridge outer tube 361 to be relatively thinner or smooth as comparedto what would be required if a fastening element was integrated into thesidewall.

For example, referring also to FIGS. 20, 25-26 and 34 , in the presentexample the dropper post assembly 300 has a fastening member in the formof a cartridge lockring 420 that includes one example of a suitablesecond engagement member in the form of outer threads 422 that are sizedand configured to mesh with the inward facing threads at the lower end312 of the post inner tube 310.

In this example, the lockring 420 is configured to be removablyinsertable in the lower end 312 of the inner tube 310, by threading andunthreading the threads 422. In addition to the second engagementmember, the lockring 420 also includes other suitable abutment andretaining features to interface with the cartridge outer tube 361 andpost inner tube 310 and also to accommodate the extension of othercartridge features, such as the cartridge rod 363 when the lockring 420is in place. In this example, the lockring 420 has an abutment surface424 that is positioned to face and bear against an opposing lowersurface on the cartridge outer tube 361 when the lockring 420 isinstalled as shown in FIG. 34 (for example). In this arrangement, whenthe fastening member, such as lockring 420, is inserted into the lowerend 312 of the inner tube 310 the abutment surface 424 bears againstlower surface 426 thereby urging the cartridge outer tube 361 axiallyupward. When the lockring 420 is tightened, the cartridge outer tube 361is compressed axially between the abutment surface 424 and the innersurface 319 at the upper end 317 of the post inner tube 310. Thisarrangement can help inhibit, and preferably stop any relative axialmovement between the cartridge outer tube 361 and the post inner tube310 when the lockring 420 is installed.

Optionally, the fastening member, such as the lockring 420 or analogousmember, may only be configured to engage the cartridge outer tube 361 inthe axial direction. Alternatively, it may be preferable for thefastening member to also provide at least some degree of lateralalignment and/or restraint for the cartridge outer tube 361 when thefastening member is installed. This may help align the cartridge outertube 361 relative to the post inner tube 310 and/or may help keep alower end of the cartridge outer tube 361 laterally centred (orotherwise positioned) relative to the lower end 312 of the post innertube 310 when the fastening member is installed and the dropper postassembly 300 is in use. This may help prevent misalignment, bucklingand/or rattling of the cartridge 360 relative to the inner tube 310.

In the illustrated example, the lockring 420 is configured to also helplaterally constrain the movement of at least the lower end 406 of thecartridge outer tube 361 relative to the post inner tube 310. In thisexample, the lockring 420 has a lateral alignment member in the form ofa captive sidewall 428 that extends axially away from the abutmentsurface 424 by a captive wall height 430. Together, the abutment surface424 and captive sidewall 428 cooperate to least partially define a tuberecess 432 at the upper end of the lockring 420 that is sized and shapedto closely receive and to accommodate the lower end 406 of the cartridgeouter tube 361. When the lockring 420 is installed, as shown in FIG. 34, at least a portion of the captive sidewall 428 is located laterally(radially) between the cartridge outer tube 361 and the sidewall 310 aof the post inner tube 310.

In this arrangement, the captive sidewall 428 laterally surrounds thetube recess 432 and defines a recess diameter 434. The recess diameter434 can be any suitable diameter, and preferably is substantially thesame as an outer diameter 400 of the cartridge outer tube 361. This canhelp provide a relatively snug fit between the cartridge outer tube 361and the captive sidewall 428, and lockring 420, so that the lateralmovement of the lower end 406 of the cartridge outer tube 361 relativeto the lockring 420, and also between the lower end 406 of the cartridgeouter tube 361 the lower end 312 of the post inner tube 310 isinhibited, and preferably eliminated.

Other portions of the lockring 420 can be sized and shaped toaccommodate or receive other positions of the cartridge 360 or othercomponents of the dropper post assembly 300. For example, in thisembodiment the lockring 420 is configured as a generally annular orring-like member having a central aperture 436 through which thecartridge rod 363 can extend when the lockring 420 is in place. That is,the aperture 436 a rod aperture that is sized to laterally surround andaxially receive the cartridge rod 363 when the lockring 420 is inserted.In this configuration, the abutment surface 424 is configured as anannular or ring-like surface that at least partially laterally surroundsthe rod aperture 436. While the abutment surface 424 is shown as agenerally continuous surface in the illustrated example it couldalternatively include gaps or other non-uniform features.

Preferably, the lockring 420, or other fastening member, can beconfigured so that when it is installed within the assembly 300 it is atleast partially nested within the interior of the post inner tube 310.This may help reduce the overall axial length of the combination of thepost inner tube 310 and the cartridge outer tube 361 and the associatedfastening members. Reducing the overall, assembled length of thesecomponents may help reduce the overall size of the assembly 300 and mayhelp facilitate desired drop lengths and performance. More preferably,at least 50%, 60%, 70%, 80%, 90%, 95% and/or 100% of the fasteningmember can be axially nested within the interior of the post inner tube310 when the fastening member is installed.

For example, in this embodiment the lockring 420 is configured so thatthe threads 422 are disposed toward a lower end 440 of the lockring 420and the abutment surface 424 is disposed axially toward an opposing,upper end 442 of the lockring 420. In this arrangement the abutmentsurface 424 is axially between the ends 440 and 442 and is axially aboveand inboard from the threads 422 when the lockring 420 is in use.

With the threads 422 located toward, and preferably at the lower end440, the lockring 420 is configured so that the entire lockring 420 isnested axially within the post inner tube 310 when it is installed. Thatis, the lockring 420 is located such that it is located above orintersects a plane 446 (FIG. 34 ) that is defined by the lower face/endof the post inner tube 310. In other arrangements portions of thelockring 420 could extend below the plane 446.

To help install and remove the lockring 420 the post assembly caninclude a suitable driving tool that is compatible with the lockring420. A convention screwdriver or the like may not be the mostappropriate driving tool because the lower end 440 of the lockring 420does not have solid surface. Instead, the lower end 440 includes the rodaperture 436. To help facilitate driving, in this example, an innersurface 450 of the lower end 440 of the lockring 420 includes a driveportion 452 that is configured to be engaged by a corresponding drivingtool used to secure the lockring 420 within the post inner tube 310.This drive portion 452 extends around the perimeter of a lower recess454 that has an inner diameter 456 and an axial length 458. This lowerrecess 454 can accommodate other portions of the assembly and, forexample, when the inner post tube 310 is in its retracted position atleast a portion of the actuator 340 that is at the lower end of the postouter tube 320 can be received within the lower recess 454, such thatthe lockring 420 at least partially overlaps the actuator 340 when theinner post tube 310 is retracted (such as in a configuration that is thesame as shown in FIG. 1 ). This may help provide a relatively longerdrop length/travel distance for the inner post tube 310 as compared toan arrangement in which the lockring 420 does not axially overlap withthe actuator 340.

To help ensure the lower recess remains relatively clear andunobstructed to provide the desired clearance for the cartridge rod 363and nesting of other components (such as the actuator 340), the driveportion 452 in this example includes a plurality of axially extendinggrooves 460 spaced apart from each other around a perimeter lower recess454. To engage the grooves 460 of the drive portion 452, a compatibledriving tool, such as tool 462, can have a plurality of correspondingtool splines 464 designed to engage the grooves 460 and a mountingportion 466 that is configured to be engaged by a driver (not shown),such as a wrench, spanner wrench, fingers, pliers/grips/channel locks, aratchet or the like. Like lockring 420, the drive tool 462 preferablyincludes an axial aperture 470 that extends through the body of thedrive tool 462. The aperture 470 is sized to allow the cartridge rod 363to pass through the drive tool 462 when it is engaged with the lockring420. When the splines 464 are engaged with the grooves 460, the aperture470 in the drive tool 462 is registered with the rod aperture 436 in thelockring 420 and the cartridge rod 363 can extend through both.

Referring also to FIGS. 29 and 30 , to insert or remove the springcartridge assembly 360 from the post inner tube 310 when using thedropper post assembly 300, the cartridge outer tube 361 can be axiallyinserted into the open, lower end 312 of the post inner tube 310. Withthe cartridge outer tube 361 inserted, the lockring 420 and drive tool462 can be slide along the length of the cartridge rod 363 until thelockring 420 reaches, and engages, the threads 408 on the post innertube 310. The lockring 420 can then be tightened, and the drive tool 462removed by axially sliding it down the length of the cartridge rod 363.This can create an inner tube subassembly that includes at least thepost inner tube 310, the cartridge 360 and lockring 420, and optionallycan include the seat clamp 350. Subassembly can now be inserted intoouter tube 320 and secured to actuator 340 is the typical manner.Referring to FIG. 30 which shows the lockring 420 installed and nestedwithin the post inner tube, the lower end 312 of the inner post tube 310can then be inserted into the post outer tube 320 and the collar 330 canbe tightened to secure the assembly together. The actuator 340 can beattached to the lower end of the post outer tube 320 in a manner whereit can engage the cartridge rod 363 and actuator rod 364 as describedherein. In this configuration, the lockring 420 can be inserted andremoved from the lower end 312 of the post inner tube 310 independentlyof, and without requiring modification of the seat clamp assembly 350.With outer tube 320 installed on inner tube 310 and fastened to collar330 but with actuator 340 removed from rod 363, lockring 420 isaccessible through the lower end of lower tube 320 when lower tube 320is slide towards the upper end of inner tube 310.

Alternatively, in other configurations the second engagement member canbe provided as part of the cartridge outer tube 361, and optionally maybe integrally formed therewith. Referring, for example, to FIG. 39 , analternative configuration of the locking spring cartridge assembly 360 ais configured to include a second engagement member in the form ofthreads 410 that are formed in the outer surface of the outer cartridgetube 361 and can threadingly engage the threads 408 on the inside of thelower end 312 of the inner post tube 310. In this arrangement, the outercartridge tube 361 can be axially inserted into the lower end 312 of thepost inner tube 310 and rotated until its threads 410 have threaded intothe thread 408 at which point the spring cartridge assembly outer tube361 can be generally rotationally and axially fixed relative to the postinner tube 310. To remove the spring cartridge assembly 360, thecartridge outer tube 361 can be unthreaded from the thread 408 and thespring cartridge assembly 360 can be axially withdrawn from the postinner tube 310.

Referring again to FIGS. 17-20 and 31-33 , in this arrangement, both theinner tube 310 and outer tube 320 are elongate, tubular members thatextend along a post axis 302. In this example, the inner tube 310 isconfigured to slide telescopically within the outer tube 320 between aretracted position and an extended position (FIGS. 17-19 , for example).The inner tube 310 includes a lower end 312 that is sized to fit withinthe outer tube 320 and that is intended to be retained within the outertube 320 in both the retracted and extended configurations. The innerpost tube 310 also has sidewall 310 a with an inner wall surface 311 anddefines an inner tube outer diameter 313 that is sized to fit within thepost outer tube 320.

Configuring the assembly such that the fastener used to secure thecartridge outer tube 361 is located toward the lower end 312 of the postinner tube 310, rather than at its upper end 317, can help facilitatethe use of different interior surface features on tube 310 than wereshown on post inner tube 110. For example, in this embodiment, the innerwall surface 311 preferably includes at least two regions or portionsthat have different respective inner diameters (and therefore differentwall thicknesses if a constant outer diameter 313 is used) and canengage, or not engage, with the cartridge 360 in different ways, andoptionally can have different internal diameters and wall thicknesses.

For example, the post inner tube 310 in this example includes an uppercaptive portion 380 disposed toward its upper end 317 and the sidewall310 a of the inner post tube 310 has a captive sidewall portion 382 thathas a first, captive inner diameter 314 a and therefore defines acorresponding captive wall thickness 384 in the lateral direction, whichin this example is a difference between the outer diameter 313 and thecaptive inner diameter 314 a. The captive sidewall portion 382 has anaxial length 480 (FIG. 32 ) and, together with the inner surface 319 ofthe upper end wall cooperates to define an upper cartridge pocket 482.

The captive inner diameter 314 a is preferably sized so that is slightlylarger than the outer diameter 400 of the cartridge outer tube 361, andpreferably is substantially the same as the outer diameter 400. This canallow the upper end 404 of the cartridge outer tube 361 to be axiallyinserted into the upper cartridge pocket 482 and be generally snuglyreceived by the captive sidewall portion 382. When the upper end 404 ofthe cartridge outer tube 361 is fully inserted in this manner, i.e.,when the lockring 420 is tightened, the upper cap surface 402 can bearagainst the inner surface 319 to inhibit axial movement of the cartridgeouter tube 361, and the captive sidewall portion 382 can engage thecartridge outer tube 361 to inhibit lateral movement of the upper end404. With the cartridge outer tube 361 inserted in this manner and withthe lockring 420 installed, both the upper end 404 and lower end 406 ofthe cartridge outer tube 361 are both axially and laterally constrainedrelative to the post inner tube 310. Because cartridge outer tube 361 isconstrained by captive diameter 314 a on the post inner tube 310 and byrecess diameter 434, both of which are smaller than clearance diameter314 b, cartridge 360 is at less buckling risk when loaded than prior artdropper 960 configuration described herein.

The inner surface 319 and upper cap surface 402 are preferablycomplimentary to each other such that they can interface/abut in adesired manner. While both surfaces 319 and 402 are shown as flat planarsurfaces in this example, other complimentary arrangements are possible.

However, instead of having a constant inner diameter along its length,the post inner tube 310 includes a second, clearance portion 490 thathas a different inner diameter 314 b (FIG. 33 ) that is larger than thediameter 314 a and preferably is larger than the outer diameter 400 ofthe cartridge outer tube 361. In this configuration, the wall thickness492 of the clearance portion 490 is less than the thickness 384 of thecaptive portion, which can reduce the amount of material used to createthe post inner tube 310 and may reduce its weight. This arrangement alsocreates a generally annular gap 494 between the cartridge outer tube 361and clearance portion 490, that has a gap width 496.

Optionally, as shown in this embodiment, the clearance portion 490 canextend to the lower end 312 of the post inner tube 310 and in thisexample, the inner diameter 314 b is substantially the same as the outerdiameter 498 (FIGS. 29 and 34 ) of the lockring 420 to allow thelockring 420 to be inserted. In this arrangement, the captive diameter314 a can be the smallest internal diameter of the post inner tube 310,and the clearance diameter 314 b is the largest internal diameter and isbelow the captive diameter 314 a.

Preferably, the interior of the post inner tube 310 is configured sothat its internal diameter remains generally constant or widens towardits lower end 312, and it is generally free from undercuts or regions inwhich an inner diameter at a lower portion is smaller than an innerdiameter of a relatively higher portion. Configuring the post inner tube310 in this manner may help simplify manufacture of the post inner tube312.

Optionally, to help fill a portion of the gap 494 a bumper 500 can beprovided, having a bumper diameter 502 (FIG. 29 ) that fits between thecartridge outer tube 361 and clearance portion 490. The bumper 500 canhelp reduce rattling and/or lateral movement of a central portion of thecartridge outer tube 361 relative to the post inner tube 360, and may beformed from any suitable material, including materials like plastic,metal, rubber, foam, wood and the like that may also help dampervibrations and/or reduce noise. The bumper 500 may be formed from thesame material or a different material than the cartridge outer tube 361and may be either integrally formed with the cartridge outer tube 361(if made of the same material) or may be a separate member that isconnectable, and optionally removable from the cartridge outer tube 361.Different bumpers 500, with different diameters 502, could be used incombination with a common cartridge outer tube 361 to help facilitatethe desired fit between the cartridge outer tube 361 and post innertubes having different internal diameters and configurations.

Referring to FIGS. 35-38 , another example configuration of the dropperpost assembly 300 is shown, with a relatively longer post inner tube310L and a relatively longer post outer tube 320L and using lockingspring cartridge assembly 360L. The post inner tube 310L and a postouter tube 320L are analogous to post inner tube 310 and a relativelylonger post outer tube 320 and can include the features described hereinand are annotated using like reference characters. One difference withthis example is that because the tube inner post 310L is longer, it canhave a longer travel distance/drop length and it may need to be somewhatstronger/stiffer than the post inner tube 310. Therefore, in thisexample the post inner tube is 310L is configured so that its uppercaptive portion 380 has the same configuration as the captive portion380 on post inner tube 310 and the sidewall 310 a of the inner post tube310L has a captive sidewall portion 382 that has a first, captive innerdiameter 314 a that can be the same as the diameter 314 a in post innertube 310, and therefore defines a corresponding captive wall thickness384 in the lateral direction. The captive inner diameter 314 a in thisexample is preferably sized so that is slightly larger than the outerdiameter 400 of the cartridge outer tube 361L, and preferably issubstantially the same as the outer diameter 400.

However, to help provide a stronger post, the clearance section 490 ofpost inner tube 310L a different inner diameter 314 b that is largerthan the diameter 314 a and preferably is larger than the outer diameter400 of the cartridge outer tube 361L but is smaller than thecorresponding diameter 314 b in the shorter, post inner tube 310. Inthis configuration, the wall thickness 492 of the clearance portion 490is less than the thickness 384 of the captive portion but is greaterthan the clearance wall of the shorter, post inner tube 310 to allow formore material to be used to create the post inner tube 310L and mayincrease its strength. This arrangement also creates a generally annulargap 494 between the cartridge outer tube 361L and clearance portion 490,that has a gap width 496 that is narrower than the corresponding width496 in the shorter, post inner tube 310. The diameter 314 b of theclearance portion 490 of the longer post inner tube 310L is stillpreferable larger than the outer diameter 400 of the cartridge outertube 361L to help facilitate axial insertion of the cartridge outer tube361L. However, the diameter 314 b is, in this example, smaller than theouter diameter 498 of the lockring 420 (FIG. 38 ). In this arrangement,the lockring 420 cannot fit within the clearance portion 490.

Therefore, to help accommodate the lockring 420, the post inner tube310L includes a third section/portion at its lower end 312 that can bereferred to as a fastener region/portion 506 that is at the lower end ofthe longer post inner tube 310L. In this configuration, the clearanceportion 490 is axially between the captive portion 380 and the fastenerportion 506. The fastener portion 506 has an internal diameter 314 cthat is larger than the diameters 314 a and 314 b in this example anddefines a wall thickness 510 that is less than the wall thicknesses 384and 392. Optionally, as shown in this embodiment, the fastener portion506 can extend from the lower edge of the clearance portion 490 to thelower end 312 of the post inner tube 310L and in this example, the innerdiameter 314 c is substantially the same as the outer diameter 498 ofthe lockring 420 to allow the lockring 420 to be inserted. In thisarrangement, the captive diameter 314 a can be the smallest internaldiameter of the post inner tube 310, and the clearance diameter 314 b isan intermediary diameter and the diameter 314 c is the largest internaldiameter within the longer post inner tube 310L.

Preferably, the interior of the post inner tube 310L is also configuredso that its internal diameter widens toward its lower end 312, and it isgenerally free from undercuts or regions in which an inner diameter at alower portion is smaller than an inner diameter of a relatively higherportion. That is, the post inner tube 310L is configured so that 314 cis larger than 314 b, and 314 b is larger than 314 a. Configuring thepost inner tube 310L in this manner may help simplify manufacture of thepost inner tube 312.

Referring to FIGS. 19 and 35 , a post assembly 300 with a relativelyshorter post inner tube 310 can be compared to the post assembly havingthe relatively longer post inner tube 310L. As described herein, due atleast in part to external design constraints and a desire for bothversions of the post assembly 300 to be compatible with the same type ofbicycle frame, and to use the same collar 330 and well as other assemblyparts, the outer diameters 313 of the inner post tubes 310 and 310L aresubstantially the same. In these examples, when the inner post tubes 310and 310L are in their extended positions (FIGS. 19 and 35 ), they eachhave different exposed lengths 512 and 512L, which can also be describedas the travel or drop length, with 512L being greater than 512. Becauselong travel version 310L has a longer drop, exposed tube length 512L isgreater that exposed length 512 and therefore the forces experienced bythe post inner tubes 310 and 310L during riding can be different. Ingeneral, the “torque” or “moment” can be described as Moment (M) equalsforce (F) multiplied by distance (D) or:M=F×D

When the post inner tubes 310 and 310L, having different drop lengthoptions 512 and 512L, are loaded with the same rearward force F_(x), amaximum moment is located at the lowest exposed portions 514 and 514L(respectively) of the sidewalls of the post inner tubes 310 and 310Lthat are just above and proximate the collar 330 and upper end of thepost lower tubes 320 and 320L. In the case, length 512 can berepresented as D1 and length 512L can be represented as D2, where:

M₁ = F × D₁ M₂ = F × D₂

Because 512L is larger than 512, M₂ is also larger than M₁ for a givenfor force F_(x).

Bending stress experienced by the post inner tubes 310 and 310L canfurther be defined as Stress (σ)=Moment (M)×the perpendicular distancefrom the outermost fiber to the neutral axis (c) divided by Moment ofinertia (I) or

$\sigma = \frac{Mc}{I}$

For a given family of generally analogous dropper post assemblies (suchas the assemblies shown herein) it can be preferable in somecircumstances that the maximum bending stress for all drop lengths issubstantially the same. This may help ensure that all drop lengths (suchas 512 and 512L and other variations) are strong enough to resist forceF_(x) and that relatively lower amounts of unnecessary, extra weight(for example from extra post inner tube 310 material) is carried on anyof the variations where it is not needed. For the maximum stress on theshorter post inner tube 310 to be equal to the maximum stress on thelonger post inner tube 512L the following relation is applied:

$\frac{M_{1}c_{1}}{I_{1}} = \frac{M_{2}c_{2}}{I_{2}}$

In the equation above the perpendicular distance from the outermostfiber to the neutral axis (c) is equal to half of the external diameters313 at their respective exposed portions 514 and 514L. because diameters313 are equal, c₁ and c₂ are also equal. The equation thus simplifiesto:

$\frac{M_{1}}{I_{1}} = \frac{M_{2}}{I_{2}}$

Because M₂ is larger than M₁ for the above equation to be equal I₂ isalso larger than I₁. In general, Moment of inertia (I) for a hollowcylinder is defined as

$I = {{\pi\frac{d_{o}^{4}}{64}} - {\pi\frac{d_{i}^{4}}{64}}}$

Where d_(o) equals outer diameter and d_(i) equals inner diameter. Inorder for I₂ to be larger than I₁ the following relation applies:

${{\pi\frac{d_{o1}^{4}}{64}} - {\pi\frac{d_{i1}^{4}}{64}}} < {{\pi\frac{d_{o2}^{4}}{64}} - {\pi\frac{d_{i2}^{4}}{64}}}$

Because outer diameters 313 are the same, d_(o1) equals d_(o2) and theequation can be simplified to:

d_(i1) > d_(i2)

In other words, for the maximum bending stress at the lowest exposedportions 514 and 514L of inner tubes 310 and 310L to be substantiallyequal, the inner diameter 314 b of inner tube 310 of shorter dropperlength option 512 must be larger than inner diameter 314 b of inner tube310L of longer dropper length option 512L. While the innercross-sectional shapes of the post inner tubes are illustrated as beingcircular, other cross-sectional shapes can be used and analogousstrength and stiffness calculations can be used. For example, while itmay be preferred for the captive portions to have a circular shape (tomatch the cartridge outer tube 361) at least some of the clearanceportions may have a different, non-circular shape. That is, instead ofbeing a circle, the diameter 314 b may instead represent the minor axisof an oval/ellipse and therefore the Ix at a lower portion of 512 issmaller for upper tube 310 than the Ix at a lower portion of 512L ofupper tube 310L.

Configuring the components in this manner can allow multiple differentvariations of the dropper post assemblies to be manufactured in a commonproduct line or family of products using a variety of shared/commoncomponents. For example, as described herein the teachings herein canfacilitate the production of aa given dropper post in a family ofdropper posts where at least some, and preferably most or optionally allcomponents are shared between the models except upper tube 310/310L,lower tube 320/320L and cartridge 360/360L and where the diameter 314 bof tube 310 is larger than diameter 314 b of tube 310L.

Referring to FIGS. 40-43 , the interior features of this example of thelocking gas spring cartridge assembly 360 are described. The springcartridge assembly 360 operates in an analogous manner to cartridge 160and like features are described using like reference characters indexedby 200.

In this example, fixedly attached to sliding surface 391 are upper sealhead 392 and lower seal head 393, which together help seal in theinterior of the cartridge outer tube 361 and substantially fluidlyisolate the interior of the cartridge outer tube 361 from thesurrounding environment (at least with a sufficient degree ofsealing/isolation to facilitate the operation of the locking springcartridge assembly 360 as described herein).

Within the interior of the cartridge outer tube 361 a piston assembly isprovided to separate the interior of the cartridge outer tube 361 intotwo different chambers, and to help facilitate the translation of thecartridge outer tube 361 as described. The piston assembly can be of anysuitable configuration that can operate as described herein. A valvemechanism is also preferably provided that can selectably allow fluidcommunication between the chambers on opposite sides of the pistonassembly, as this can be used to lock and unlock the locking springcartridge assembly 360. The valve, and related fluid flow path regions,can be of any suitable configuration.

To help reduce the overall size of the locking spring cartridge assembly360, it may be preferable to integrate a suitable valve mechanism withinthe piston assembly, as is shown in the present example that includes apiston valve 394 attached to the upper end 363 a of a cartridge rod 363that can extend from the piston valve 394 to the actuator assembly 340.The piston valve 394 is sized to generally fill the cartridge outer tube361, is positioned axially between the upper and lower cartridge sealheads 392 and 393 and has a sealing portion that is positioned oppositeand configured to seal against the sliding surface 391 and includes abody-sliding-surface o-ring 398 (or other suitable translatable sealingmember). The piston valve 394, in this example, also includes a valvebody 395, a plunger 396 that can move relative to the valve body 395, abody-piston o-ring 397, and valve cap 399. In this embodiment the valvebody 395 defines a corresponding valve body channel 395 a (see also FIG.22 ) and a valve inner pathway 395 b (FIG. 43 ). The plunger 396includes a seal surface 396 a, that can seal against the valve body 395(e.g., against o-ring 397 in this example) to inhibit fluid flow throughthe piston valve, and neck portion 396 b.

In this arrangement, the piston 394 divides the interior of thecartridge outer tube 361 into two operating chambers that can be fluidlyisolated from each other while the locking spring cartridge assembly 360is in use to selectably lock and unlock the locking spring cartridgeassembly 360. For example, when the operating chambers are fluidlyisolated from each other (e.g., the valve is closed—FIGS. 40 and 41 )the locking spring cartridge assembly 360 can be considered to be in alocked configuration and will resist movement of the cartridge outertube 361 and seat post inner tube 310. In contrast, when the operatingchambers are fluidly connected, such as by activating the piston valve394 and allowing fluid (liquid) to pass through the piston 394 and flowbetween the operating chambers (FIGS. 42 and 43 ), the locking springcartridge assembly 360 can be considered to be in an unlockedconfiguration, and will facilitate the relative movement of thecartridge outer tube 361 and seat post inner tube 310 relative to theouter tube 320. As described herein, when the locking spring cartridgeassembly 360 is in use, and the piston valve 394 is opened, thecartridge outer tube 361 can translate relative to the piston 394 toallow the seat post inner tube 310 to translate relative to the outertube 320.

As described herein, a first, of the operating chambers is chamber 381,is located axially between the piston valve 394 and the lower seal head393 and is laterally bounded by the sliding surface 391 and isconfigured to contain only, or at least substantially only liquid, suchas the oil described herein, rather than a mixture of liquid and gas orother material and can also be referred to as a liquid chamber. When thelocking spring cartridge assembly 360 is in use within the seat post 300in the orientation illustrated these Figures (which is also theorientation of the locking spring cartridge assembly 360 when it is inuse on a bicycle) the chamber 381 can be referred to as a lower chamber381, but it is understood that the term lower is used for convenienceand is not intended to limit the orientation of the locking springcartridge assembly 360 when in use.

In the present example, the other, or second, operating chamber ischamber 382 which is located axially between the piston valve 394 andthe upper seal head 392 and is also laterally bounded by the slidingsurface 391. Because of its relative location within the locking springcartridge assembly 360 as illustrated, the second chamber 382 can bereferred to as an upper chamber 382. In contrast to lower chamber 381,the upper chamber 382 is preferably configured to contain a mixture ofoil (or other suitable liquid) and pressurized air (or other suitablegas), instead of containing only oil/liquid, and can be referred to as agas/liquid chamber.

Under the intended operating conditions of the locking spring cartridgeassembly 360 the oil and air (or other liquid and gas) in the gas/liquidchamber 382 with tend to separate from each other due the differences intheir densities and mechanical properties, such that an air/oilinterface or boundary 383 is defined between piston valve 394 and upperseal head 392 within chamber 382. In this arrangement, the gas/liquidchamber 382 will have a lower layer or region containing oil occupyingthe space located axially between the boundary 383 and the piston valve394, and an upper layer or region that is above the oil layer andboundary 383 and is located axially between the boundary 383 and theupper seal head 392. When the piston valve 394 is actuated and its valveis open, fluid communication between the liquid layer within chamber 382and the liquid within the lower chamber 381 is established.

In these illustrated examples, if, while the piston valve 394 is closedand the spring cartridge assembly is considered to be locked, inner tube310 is urged towards its retracted position with a force that less thandegassing Force F_(D) (as described herein), inner tube 310 will remainaxially fixed with outer tube 320. This can help facilitate the desiredrider experience and the desired feeling of solidity and stability ofthe dropper post. However, when the force urging the inner tube 310toward its retracted position exceeds the degassing force F_(D) (and anyassociated losses, friction forces and the like), dissolved air ispulled out of solution within lower chamber 381. Small air bubbles 385may form in lower chamber 381 and this can allow a relatively smallamount of relative axial movement of the inner tube 310 relative to thepiston valve 394, described as the overload cushion distance herein andthat may be at least, and optionally can be between about 1 mm and 40 mmor between 10 mm and about 30 mm, and can between about 0% and about 20%of the travel length of the post inner tube 310. This axial movementtherefore acts as a cushion if a rider overloads the post, such as whilewhen riding or during a crash. Once the force urging inner tube 310toward the retracted position drops back below the degassing forceF_(D), the air bubbles 385 can go back into solution and the inner tube310 returns to its original height.

It is possible however, in some situations, that the air bubbles 385 maynot all return to solution or that additional air bubbles may collect inthe lower chamber 381 over time. For example, a leak in the system couldallow air to enter the lower chamber 381 or operating the springcartridge assembly 300 in sideways or inverted orientations may allowgas from the upper chamber 382 to enter the lower chamber 381 when thevalve 394 is open. Gas may also be introduced into the lower chamber 381during maintenance or other analogous activities. While a relativelysmall amount of gas bubbles 385 may provide some desirable cushioningeffects, having too much gas (i.e., too many bubbles 385) in the lowerchamber 381 may affect the stiffness or feel of the dropper postassembly in an undesirable manner.

In the examples illustrated herein, configuring the dropper postassembly 300 with the combined gas and air chamber as the upper chamber382, and the lower chamber 381 as the lower chamber when the postassembly 300 is in its normal orientation (e.g., when the bicycle isupright and rolling on its wheels) can also enable the spring cartridgeassembly 300 to be generally self-purging/correcting or self-bleeding.That is, as shown in FIGS. 41 , when the valve 394 is closed the gasbubbles 385 are trapped in the lower chamber 381. However, when thevalve 394 is opened (FIG. 43 ), such as when the dropper post assembly300 is in normal use, the flow paths are open and the gas bubbles 385will tend to travel upwardly, through the valve 394 from the lowerchamber 381 to the upper chamber 382 due to their relative buoyancy ascompared to the liquid, and/or if they are entrained with portions ofthe liquid that is also travelling thorough the valve 394. The gasbubbles 385 that reach the upper chamber 382 can then continue floatingupwardly and collect in the lay of gas that is above the interface 383.In this arrangement, each time the dropper post assembly 100, 200 or 300is triggered (e.g. when their respective cartridges 160, 260 and 360 areunlocked) gas bubbles 385 that were trapped in the lower chamber 381 canmigrate to the upper chamber 382, thereby automatically resetting thebalance of gas and liquid within the cartridges 160, 260 and 360, andself-bleeding the gas bubbles out of the lower, liquid-only chamber intothe upper, mixed gas and liquid chamber where the presence of gas willnot alter the intended performance of the cartridge assembly. That is,in the illustrated example the first chamber 381 contains, and isintended to contain, substantially only a liquid and the second chamber382 contains, and is intended to contain, a mixture of a liquid and agas. In this arrangement, when the dropper post assembly is oriented sothat the second chamber 382 is above the first chamber 381 (as shown)the spring cartridge assembly operates as a self-bleeding cartridge, inwhich when the valve 391 is in its open position gas contained in thefirst chamber 381 (if any) escapes through the valve 391 and iscollected in the second chamber 382. Configuring the dropper postassembly 300 may help the spring cartridge assembly 360 automaticallybleed/purge gas bubbles from the lower chamber 381 into the upperchamber 382 each time the spring cartridge assembly is triggered and thepiston valve 394 is opened. This self-bleeding configuration can helpreduce the accumulation of gas within the lower chamber 381 (that may beintended to contain primarily only liquid in some arrangements) whilethe dropper post assembly 300 is in use and may reduce and/or eliminatethe need for the spring cartridge assembly to be opened or accessed by aservice technician for repair or servicing.

In the illustrated examples of dropper post assembly 300, the whereinthe spring cartridge 360 is configured as a generally sealed,independent locking spring cartridge in which the cartridge outer tube361 is separate from the walls of the post inner tube 310. In thisarrangement, the spring cartridge assembly 360 is insertable andremovable from within the post inner tube 310 in its charged/pressurizedconfiguration and is operable independently of the inner tube 310 sothat when the spring cartridge assembly 360 is axially removable via thelower end 312 of the inner tube 310 (for example, when the secondengagement member is disengaged from the tube engagement member), thespring cartridge assembly biasing mechanism remains operable and doesnot need to be opened, discharged or otherwise modified. This may helpsimplify assembly and maintenance of the seat post assembly 300.

While this invention has been described with reference to illustrativeembodiments and examples, the description is not intended to beconstrued in a limiting sense. Thus, various modifications of theillustrative embodiments, as well as other embodiments of the invention,will be apparent to persons skilled in the art upon reference to thisdescription. It is therefore contemplated that the appended claims willcover any such modifications or embodiments.

All publications, patents and patent applications referred to herein areincorporated by reference in their entirety to the same extent as ifeach individual publication, patent, or patent application wasspecifically and individually indicated to be incorporated by referencein its entirety.

We claim:
 1. A dropper post assembly for supporting a bicycle seat, thedropper post assembly comprising: a) an outer tube extending axiallyalong a post axis between a lower end and an upper end; b) an inner tubeextending axially between i. an upper end that is connectable to abicycle seat; and ii. a lower end that is disposed within the outer tubeand comprises a tube engagement member, the inner tube being axiallymovable relative to the outer tube between an extended position and aretracted position; c) a spring cartridge assembly configurable in anunlocked configuration in which the spring cartridge assembly biases theinner tube toward its extended position and a locked configuration, thespring cartridge assembly comprising: i. a cartridge tube providing acylinder and being disposed within and movable with the inner tube, thecartridge tube extending between an upper end disposed at the upper endof the inner tube and a lower end that is disposed at the lower end ofthe inner tube, the cartridge tube being axially removable via the lowerend of the inner tube when the second engagement member is disengagedfrom the tube engagement member and the spring cartridge assemblyremains operational when removed from the inner tube; ii. a lower sealassembly disposed at a lower end of the cartridge tube and sealing alower end of the cylinder; iii. a piston movably received within thecylinder to provide a first chamber defined between the piston and thelower seal assembly and disposed on a lower side of the piston, and asecond chamber between the piston and an upper end of the cylinder anddisposed on an opposing, upper side of the piston, whereby moving theinner tube toward the retracted position expands the first chamber, thepiston including a valve that is configurable in an open position inwhich fluid communication is established between the first chamber andsecond chamber and the spring cartridge assembly is in the unlockedconfiguration, and a closed position in which the first chamber isfluidly isolated from the second chamber and the spring cartridgeassembly is in the locked configuration; iv. a cartridge rod extendingaxially through the lower seal assembly between an inner end engagingthe piston and an outer lower end at the lower end the outer tube; andv. a second engagement member configured to releasably engage the tubeengagement member thereby fastening the cartridge tube to the lower endof the inner tube so that the cartridge tube is axially fixed to theinner tube and movable with the inner tube relative to the outer tube;d) an actuator having a body disposed adjacent the outer end of thecartridge rod and being operable to actuate the valve to change thespring cartridge assembly between the locked configuration and theunlocked configuration.
 2. The dropper post assembly of claim 1, whereinthe tube engagement member is integrally formed on an inner surface ofthe inner tube.
 3. The dropper post assembly of claim 1, wherein theupper end of the cartridge tube does not include a fastening mechanismengaging the inner tube in a manner that restrains axial movement of thecartridge relative to the inner tube.
 4. The dropper post assembly ofclaim 1, wherein an axially upper most portion of the spring cartridgeis disposed within the inner tube and does not extend axially beyond theupper end of the inner tube, whereby an entirety of the spring cartridgeis disposed axially inboard of the upper end of the inner tube.
 5. Thedropper post assembly of claim 1, wherein the inner tube comprises anupper end wall that covers the upper end of the inner tube and thecartridge tube comprises an axially facing upper cap surface thatopposes the upper end wall when the cartridge tube is disposed withinthe inner tube, wherein the upper cap surface and upper end wall arecomplimentary to each other and generally planar and the cartridge tubeis located axially inboard of the upper end wall.
 6. The dropper postassembly of claim 1, further comprising an openable seat clamp assemblyconnected to the upper end of the inner tube and configured toreleasably retain a bicycle seat, and wherein the second engagementmember is disengageable from the tube engagement member so that thespring cartridge can be removed from the inner tube without opening theseat clamp assembly.
 7. The dropper post assembly of claim 1, whereinwhen the spring cartridge is axially removable via the lower end of theinner tube after disengaging the second engagement member from the tubeengagement member and wherein the cylinder remains sealed and the springcartridge assembly remains operable when the spring cartridge assemblyis removed from the inner tube.
 8. The dropper post assembly of claim 1,further comprising a fastening member that is removably insertable inthe lower end of the inner tube, the fastening member comprising thesecond engagement member and an abutment surface, wherein when thefastening member is inserted so that the second engagement memberengages the tube engagement member the cartridge tube is compressedaxially between the abutment surface and the upper end of the innertube.
 9. The dropper post assembly of claim 8, wherein the fasteningmember further comprises a captive sidewall extending axially from theabutment surface and cooperating with the abutment surface to at leastpartially define a tube recess sized to accommodate the lower end of thecartridge tube, wherein when the fastening member is inserted thecaptive sidewall is disposed laterally between the cartridge tube andthe inner tube.
 10. The dropper post assembly of claim 9, wherein thecaptive sidewall surrounds the tube recess and defines a recess diameterthat is substantially the same as an outer diameter of the cartridgetube so that the and lateral movement of the lower end of the cartridgetube relative to the fastening member and the lower end of the innertube is inhibited cartridge tube is closely/snugly in the tube recess sothat when the fastening member is inserted lateral movement between thelower end of the cartridge tube and the lower end of the inner tube isinhibited.
 11. The dropper post assembly of claim 8, wherein the secondengagement member is disposed toward a lower end of the fastening memberand the abutment surface is disposed toward an opposing, upper end ofthe fastening member.
 12. The dropper post assembly of claim 11, whereinan inner surface of the lower end of the fastening member comprises adrive portion configured to be engaged by a corresponding driving toolused to secure the fastening member within the inner tube.
 13. Thedropper post assembly of claim 8, wherein when the fastening member isinserted it is at least partially axially nested within the inner tube.14. The dropper post assembly of claim 8, further comprising an openableseat clamp assembly connected to the upper end of the inner tube andconfigured to releasably retain a bicycle seat, and wherein thefastening member is insertable and removable from the inner tubeindependently from opening the seat clamp assembly, whereby the secondengagement member is disengagable from the tube engagement memberwithout opening the seat clamp assembly.
 15. The dropper post assemblyof claim 1, wherein the inner tube comprises an upper captive portion atits upper end having a first internal diameter that is substantially thesame as an outer diameter of the cartridge tube so that the upper end ofthe cartridge tube is closely/snugly received in the upper captiveportion but remains axially removable and lateral movement between thecartridge tube and the inner tube is inhibited.
 16. The dropper postassembly of claim 15, wherein the inner tube further comprises aclearance portion axially inboard from the upper captive portion andhaving a second internal diameter that is greater than the firstinternal diameter and the outer diameter of the cartridge tube, wherebyan annular gap is formed within the clearance portion between an outersurface of the cartridge tube and an opposing inner surface of the innertube.
 17. The dropper post assembly of claim 16, further comprising abumper positioned laterally between the cartridge tube and the innertube within the annular gap and inhibiting lateral movement of thecartridge tube relative to the inner tube.
 18. The dropper post assemblyof claim 17, wherein the bumper laterally encircles the cartridge tubeand has a length in the axial direction that is less than 20% of anaxial length of the cartridge tube.
 19. The dropper post assembly ofclaim 17, wherein the bumper is located within an axially middle portionof the cartridge tube, and optionally may be located at the axialmidpoint of the cartridge tube.
 20. The dropper post assembly of claim16, wherein the lower end of the inner tube further comprises anengagement region that includes the tube engagement member and has athird internal diameter that is greater than the second internaldiameter.
 21. The dropper post assembly of claim 20, wherein the innerdiameter of the inner tube increases from its upper end to its lowerend.
 22. The dropper post assembly of claim 1, wherein the innerengagement member is formed on an outer surface of the cartridge tube.23. The dropper post assembly of claim 1, wherein the first chambercontains substantially only a liquid and the second chamber contains amixture of a liquid and a gas.
 24. The dropper post assembly of claim 1,wherein when the dropper post assembly is oriented so that the secondchamber is above the first chamber the spring cartridge assemblyoperates as a self-bleeding cartridge, in which when the valve is in itsopen position gas contained in the first chamber escapes through thevalve and is collected in the second chamber.
 25. The dropper postassembly of claim 2, wherein the tube engagement member comprisesthreads formed in the inner surface of the inner tube.
 26. The dropperpost assembly of claim 13, wherein when the fastening member is insertedit is entirely axially nested within the inner tube.